-----BEGIN PRIVACY-ENHANCED MESSAGE----- Proc-Type: 2001,MIC-CLEAR Originator-Name: webmaster@www.sec.gov Originator-Key-Asymmetric: MFgwCgYEVQgBAQICAf8DSgAwRwJAW2sNKK9AVtBzYZmr6aGjlWyK3XmZv3dTINen TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB MIC-Info: RSA-MD5,RSA, VfZmucXD/7C9sau5O65uvnS7xL9mB6A6+z9Lah22OIMMgvIM3K+F/b8OXa4bV/48 OdQ6IhgyNRzgOFZlB24ixQ== 0001104659-07-050829.txt : 20070628 0001104659-07-050829.hdr.sgml : 20070628 20070628161542 ACCESSION NUMBER: 0001104659-07-050829 CONFORMED SUBMISSION TYPE: N-CSRS PUBLIC DOCUMENT COUNT: 3 CONFORMED PERIOD OF REPORT: 20070430 FILED AS OF DATE: 20070628 DATE AS OF CHANGE: 20070628 EFFECTIVENESS DATE: 20070628 FILER: COMPANY DATA: COMPANY CONFORMED NAME: TAX MANAGED MID CAP CORE PORTFOLIO CENTRAL INDEX KEY: 0001163516 IRS NUMBER: 000000000 STATE OF INCORPORATION: MA FISCAL YEAR END: 1031 FILING VALUES: FORM TYPE: N-CSRS SEC ACT: 1940 Act SEC FILE NUMBER: 811-10597 FILM NUMBER: 07947090 BUSINESS ADDRESS: STREET 1: EATON VANCE BUILDING STREET 2: 255 STATE STREET CITY: BOSTON STATE: MA ZIP: 02109 BUSINESS PHONE: 800-225-6265 MAIL ADDRESS: STREET 1: EATON VANCE BUILDING STREET 2: 255 STATE STREET CITY: BOSTON STATE: MA ZIP: 02109 FORMER COMPANY: FORMER CONFORMED NAME: TAX MANAGED MID CAP STOCK PORTFOLIO DATE OF NAME CHANGE: 20011212

0001163516 S000005250 TAX MANAGED MID CAP CORE PORTFOLIO

C000014302 TAX MANAGED MID CAP CORE PORTFOLIO

N-CSRS 1 a07-16853_2ncsrs.htm CERTIFIED SEMI-ANNUAL SHAREHOLDER REPORT

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-CSR

CERTIFIED SHAREHOLDER REPORT OF REGISTERED
MANAGEMENT INVESTMENT COMPANIES

Investment Company Act file number			811-10597

Tax-Managed Mid-Cap Core Portfolio
(Exact name of registrant as specified in charter)

The Eaton Vance Building, 255 State Street, Boston, Massachusetts					02109
(Address of principal executive offices)					(Zip code)

Alan R. Dynner The Eaton Vance Building, 255 State Street, Boston, Massachusetts 02109
(Name and address of agent for service)

Registrant’s telephone number, including area code:				(617) 482-8260

Date of fiscal year end:	October 31

Date of reporting period:		April 30, 2007

Item 1. Reports to Stockholders

Tax-Managed Mid-Cap Core Portfolio as of April 30, 2007

PORTFOLIO OF INVESTMENTS (Unaudited)

Common Stocks — 99.1%
Security	Shares		Value
Air Freight & Logistics — 1.9%
C.H. Robinson Worldwide, Inc.		18,200	$	972,972
Expeditors International of Washington, Inc.		23,300		973,940
			$	1,946,912
Airlines — 1.3%
SkyWest, Inc.		51,000	$	1,387,710
			$	1,387,710
Automobiles — 0.9%
Thor Industries, Inc.		25,000	$	995,750
			$	995,750
Capital Markets — 5.4%
A.G. Edwards, Inc.		14,800	$	1,072,260
Affiliated Managers Group, Inc.⁽¹⁾		18,800		2,211,444
Federated Investors, Inc., Class B		28,000		1,068,480
SEI Investments Co.		22,300		1,360,969
			$	5,713,153
Chemicals — 2.8%
Albemarle Corp.		35,200	$	1,494,240
RPM International, Inc.		70,000		1,488,900
			$	2,983,140
Commercial Banks — 5.0%
City National Corp.		22,000	$	1,610,840
Cullen/Frost Bankers, Inc.		21,700		1,110,389
Synovus Financial Corp.		41,600		1,312,896
TCF Financial Corp.		45,000		1,218,600
			$	5,252,725
Computer Peripherals — 1.7%
Diebold, Inc.		38,500	$	1,835,295
			$	1,835,295
Construction & Engineering — 1.6%
Jacobs Engineering Group, Inc.⁽¹⁾		33,000	$	1,664,190
			$	1,664,190

Security	Shares		Value
Construction Materials — 1.2%
Martin Marietta Materials, Inc.		9,000	$	1,312,380
			$	1,312,380
Containers & Packaging — 1.6%
Sonoco Products Co.		40,300	$	1,718,392
			$	1,718,392
Diversified Consumer Services — 0.5%
Apollo Group, Inc., Class A⁽¹⁾		11,500	$	543,950
			$	543,950
Electric Utilities — 1.7%
DPL, Inc.		56,600	$	1,774,410
			$	1,774,410
Electrical Equipment — 5.0%
AMETEK, Inc.		42,000	$	1,523,760
Cooper Industries Ltd. Class A		35,200		1,751,552
Genlyte Group, Inc. (The)⁽¹⁾		10,000		780,100
Hubbell, Inc., Class B		23,000		1,188,870
			$	5,244,282
Electronic Equipment & Instruments — 5.1%
Amphenol Corp., Class A		55,000	$	1,931,050
CDW Corp.		27,300		1,965,873
National Instruments Corp.		51,000		1,420,860
			$	5,317,783
Energy Equipment & Services — 5.5%
FMC Technologies, Inc.⁽¹⁾		29,000	$	2,055,520
Grant Prideco, Inc.⁽¹⁾		15,000		773,100
Hydril Co.⁽¹⁾		18,000		1,742,760
National Oilwell Varco, Inc.⁽¹⁾		14,000		1,187,900
			$	5,759,280
Food & Staples Retailing — 1.0%
Ruddick Corp.		36,000	$	1,081,080
			$	1,081,080

See notes to financial statements
15

Tax-Managed Mid-Cap Core Portfolio as of April 30, 2007

PORTFOLIO OF INVESTMENTS (Unaudited) CONT'D

Security	Shares		Value
Food Products — 1.8%
Hormel Foods Corp.		35,000	$	1,333,150
Tootsie Roll Industries, Inc.		19,806		574,176
			$	1,907,326
Gas Utilities — 4.8%
AGL Resources, Inc.		41,100	$	1,789,494
Piedmont Natural Gas Co., Inc.		61,200		1,615,068
Questar Corp.		17,000		1,651,210
			$	5,055,772
Health Care Equipment & Supplies — 8.8%
Beckman Coulter, Inc.		24,900	$	1,563,969
Biomet, Inc.		8,000		345,600
C.R. Bard, Inc.		15,800		1,313,454
DENTSPLY International, Inc.		45,800		1,530,178
Mentor Corp.		25,000		972,750
Respironics, Inc.⁽¹⁾		48,500		1,976,860
Varian Medical Systems, Inc.⁽¹⁾		36,000		1,519,560
			$	9,222,371
Health Care Providers & Services — 1.3%
Owens & Minor, Inc.		38,000	$	1,343,300
			$	1,343,300
Hotels, Restaurants & Leisure — 3.9%
Applebee's International, Inc.		43,000	$	1,168,740
Brinker International, Inc.		15,000		466,500
International Speedway Corp. Class A		25,200		1,244,880
Sonic Corp.⁽¹⁾		53,850		1,208,394
			$	4,088,514
Household Durables — 2.0%
Harman International Industries, Inc.		11,000	$	1,340,790
Mohawk Industries, Inc.⁽¹⁾		8,500		766,360
			$	2,107,150
Insurance — 3.7%
Cincinnati Financial Corp.		26,000	$	1,176,240
Markel Corp.⁽¹⁾		3,500		1,606,185
Protective Life Corp.		24,000		1,125,600
			$	3,908,025

Security	Shares		Value
IT Services — 2.3%
Cognizant Technology Solutions Corp., Class A⁽¹⁾		15,000	$	1,341,000
Fiserv, Inc.⁽¹⁾		20,200		1,074,034
			$	2,415,034
Machinery — 2.7%
Dover Corp.		30,300	$	1,458,036
Graco, Inc.		34,200		1,350,900
			$	2,808,936
Media — 2.4%
E.W. Scripps Co.		20,900	$	904,970
Washington Post Co. (The), Class B		2,200		1,636,800
			$	2,541,770
Multiline Retail — 1.1%
Family Dollar Stores, Inc.		37,000	$	1,178,080
			$	1,178,080
Multi-Utilities — 2.7%
NSTAR		33,000	$	1,184,700
OGE Energy Corp.		42,300		1,626,012
			$	2,810,712
Office Electronics — 1.8%
Zebra Technologies Corp. Class A⁽¹⁾		46,225	$	1,839,293
			$	1,839,293
Oil, Gas & Consumable Fuels — 3.0%
Holly Corp.		35,000	$	2,226,000
Peabody Energy Corp.		20,000		959,600
			$	3,185,600
Real Estate Investment Trusts (REITs) — 1.6%
Developers Diversified Realty Corp.		25,300	$	1,647,030
			$	1,647,030
Semiconductors & Semiconductor Equipment — 3.1%
Microchip Technology, Inc.		42,050	$	1,696,297
Varian Semiconductor Equipment Associates, Inc.⁽¹⁾		23,750		1,576,050
			$	3,272,347

See notes to financial statements
16

Tax-Managed Mid-Cap Core Portfolio as of April 30, 2007

PORTFOLIO OF INVESTMENTS (Unaudited) CONT'D

Security	Shares		Value
Software — 3.6%
ANSYS, Inc.⁽¹⁾		18,100	$	926,720
Citrix Systems, Inc.⁽¹⁾		31,500		1,026,900
Jack Henry & Associates, Inc. Class A		78,500		1,864,375
			$	3,817,995
Specialty Retail — 2.5%
O'Reilly Automotive, Inc.⁽¹⁾		45,000	$	1,602,000
Ross Stores, Inc.		32,500		1,077,375
			$	2,679,375
Tobacco — 2.7%
Universal Corp./Richmond, VA		46,000	$	2,883,280
			$	2,883,280
Trading Companies & Distributors — 1.1%
MSC Industrial Direct Co., Inc., Class A		23,000	$	1,121,020
			$	1,121,020
Total Common Stocks (identified cost $76,287,361)			$	104,363,362
Total Investments — 99.1% (identified cost $76,287,361)			$	104,363,362
Other Assets, Less Liabilities — 0.9%			$	953,272
Net Assets — 100.0%			$	105,316,634

⁽¹⁾ Non-income producing security.

See notes to financial statements
17

Tax-Managed Mid-Cap Core Portfolio as of April 30, 2007

FINANCIAL STATEMENTS (Unaudited)

Statement of Assets and Liabilities

As of April 30, 2007

Assets
Investments, at value (identified cost, $76,287,361)	$	104,363,362
Cash		715,849
Receivable for investments sold		917,760
Dividends and interest receivable		89,077
Total assets	$	106,086,048
Liabilities
Payable for investments purchased	$	667,007
Payable to affiliate for investment advisory fees		69,729
Payable to affiliate for Trustees' fees		1,160
Other accrued expenses		31,518
Total liabilities	$	769,414
Net Assets applicable to investors' interest in Portfolio	$	105,316,634
Sources of Net Assets
Net proceeds from capital contributions and withdrawals	$	77,240,633
Net unrealized appreciation (computed on the basis of identified cost)		28,076,001
Total	$	105,316,634

Statement of Operations

For the Six Months Ended
April 30, 2007

Investment Income
Dividends	$	625,330
Interest		15,158
Total investment income	$	640,488
Expenses
Investment adviser fee	$	404,807
Trustees' fees and expenses		3,620
Custodian fee		27,117
Legal and accounting services		13,802
Miscellaneous		2,157
Total expenses	$	451,503
Deduct — Reduction of investment adviser fee	$	988
Total expense reductions	$	988
Net expenses	$	450,515
Net investment income	$	189,973
Realized and Unrealized Gain (Loss)
Net realized gain (loss) — Investment transactions (identified cost basis)	$	4,127,087
Net realized gain	$	4,127,087
Change in unrealized appreciation (depreciation) — Investments (identified cost basis)	$	6,470,753
Net change in unrealized appreciation (depreciation)	$	6,470,753
Net realized and unrealized gain	$	10,597,840
Net increase in net assets from operations	$	10,787,813

See notes to financial statements
18

Tax-Managed Mid-Cap Core Portfolio as of April 30, 2007

FINANCIAL STATEMENTS CONT'D

Statements of Changes in Net Assets

Increase (Decrease) in Net Assets	Six Months Ended April 30, 2007 (Unaudited)			Year Ended October 31, 2006
From operations — Net investment income	$	189,973		$	261,470
Net realized gain from investment transactions		4,127,087			4,855,443
Net change in unrealized appreciation (depreciation) of investments		6,470,753			6,129,045
Net increase in net assets from operations	$	10,787,813		$	11,245,958
Capital transactions — Contributions	$	3,039,473		$	16,793,678
Withdrawals		(6,387,404	)		(6,253,468	)
Net increase (decrease) in net assets from capital transactions	$	(3,347,931	)	$	10,540,210
Net increase in net assets	$	7,439,882		$	21,786,168
Net Assets
At beginning of period	$	97,876,752		$	76,090,584
At end of period	$	105,316,634		$	97,876,752

See notes to financial statements
19

Tax-Managed Mid-Cap Core Portfolio as of April 30, 2007

FINANCIAL STATEMENTS CONT'D

Supplementary Data

	Six Months Ended April 30, 2007			Year Ended October 31,												Period Ended
	(Unaudited)			2006			2005			2004			2003			October 31, 2002⁽¹⁾
Ratios/Supplemental Data
Ratios (As a percentage of average daily net assets):
Expenses⁽²⁾		0.90	%⁽³⁾		0.91	%		0.91	%		0.93	%		0.99	%		1.68	%⁽³⁾
Net investment income (loss)		0.38	%⁽³⁾		0.29	%		(0.11	)%		(0.15	)%		(0.22	)%		(0.81	)%⁽³⁾
Portfolio Turnover		15	%		55	%		53	%		42	%		50	%		13	%
Total Return⁽⁴⁾		11.30	%		13.85	%		10.54	%		6.43	%		25.97	%		(14.72	)%
Net assets, end of period (000's omitted)	$	105,317		$	97,877		$	76,091		$	67,130		$	46,112		$	17,149

⁽¹⁾ For the period from the start of business, March 1, 2002, to October 31, 2002.

⁽²⁾ The investment adviser waived a portion of its investment advisory fee (equal to less than 0.01% of the average daily net assets for the six months ended April 30, 2007 and for each of the years ended October 31, 2006, 2005, and 2004). A portion of the waiver was borne by the sub-advisor.

⁽³⁾ Annualized.

⁽⁴⁾ Total return is not computed on an annualized basis.

See notes to financial statements
20

Tax-Managed Mid-Cap Core Portfolio as of April 30, 2007

NOTES TO FINANCIAL STATEMENTS (Unaudited)

1 Significant Accounting Policies

Tax-Managed Mid-Cap Core Portfolio (the Portfolio) is registered under the Investment Company Act of 1940, as amended (the 1940 Act), as a diversified open-end management investment company. The Portfolio, which was organized as a trust under the laws of the State of New York on December 10, 2001, seeks to achieve long-term, after-tax returns by investing in a diversified portfolio of common stocks of mid-cap companies. The Declaration of Trust permits the Trustees to issue interests in the Portfolio. At April 30, 2007, the Eaton Vance Tax-Managed Mid-Cap Core Fund and the Eaton Vance Tax-Managed Equity Asset Allocation Fund held 33.1% and 66.9% interests in the Portfolio, respectively. The following is a summary of significant accounting policies consistently followed by the Portfolio in the preparation of its financial statements. The policies are in conformity with accounting principles generally accepted in the United States of America.

A Investment Valuation — Securities listed on a U.S. securities exchange generally are valued at the last sale price on the day of valuation or, if no sales took place on such date, at the mean between the closing bid and asked prices therefore on the exchange where such securities are principally traded. Equity securities listed on the NASDAQ Global or Global Select Market System generally are valued at the official NASDAQ closing price. Unlisted or listed securities for which closing sales prices or closing quotations are not available are valued at the mean between the latest available bid and asked prices, or, in the case of preferred equity securities that are not listed or traded in the over-the-counter market, by an independent pricing service. Exchange-traded opti ons are valued at the last sale price for the day of valuation as quoted on the principal exchange or board of trade on which the options are traded or, in the absence of sales on such date, at the mean between the latest bid and asked prices therefore. Futures positions on securities and currencies generally are valued at closing settlement prices. Short-term debt securities with a remaining maturity of 60 days or less are valued at amortized cost. If short-term debt securities are acquired with a remaining maturity of more than 60 days, they will be valued by a pricing service. Other fixed income and debt securities, including listed securities and securities for which price quotations are available, will normally be valued on the basis of valuations furnished by a pricing service. Foreign securities and currencies are valued in U.S. dollars, based on foreign currency exchange rate quotations supplied by an independent quotation service. The daily valuation of exchange-traded foreign securities generally i s determined as of the close of trading on the principal exchange on which such securities trade. Events occurring after the close of trading on foreign exchanges may result in adjustments to the valuation of foreign securities to more accurately reflect their fair value as of the close of regular trading on the New York Stock Exchange. When valuing foreign securities that meet certain criteria, the Trustees have approved the use of a fair value service that values such securities to reflect market trading that occurs after the close of the applicable foreign markets of comparable securities or other instruments that have a strong correlation to the fair-valued securities. Investments held by the Portfolio for which valuations or market quotations are unavailable are valued at fair value using methods determined in good faith by or at the direction of the Trustees of the Portfolio considering relevant factors, data and information includ ing the market value of freely tradable securities of the same class in the principal market on which such securities are normally traded.

B Income — Dividend income is recorded on the ex-dividend date for dividends received in cash and/or securities. However, if the ex-dividend date has passed, certain dividends from foreign securities are recorded as the Portfolio is informed of the ex-dividend date. Withholding taxes on foreign dividends and capital gains have been provided for in accordance with the Portfolio's understanding of the applicable countries' tax rules and rates. Interest income is recorded on the accrual basis.

C Federal Taxes — The Portfolio has elected to be treated as a partnership for federal tax purposes. No provision is made by the Portfolio for federal or state taxes on any taxable income of the Portfolio because each investor in the Portfolio is ultimately responsible for the payment of any taxes on its share of taxable income. Since at least one of the Portfolio's investors is a regulated investment company that invests all or substantially all of its assets in the Portfolio, the Portfolio normally must satisfy the applicable source of income and diversification requirements (under the Internal Revenue Code) in order for its investors to satisfy them. The Portfolio will allocate, at least annually among its investors, each investor's distributive share of the Portfolio' s net investment income, net realized capital gains, and any other items of income, gain, loss, deduction or credit.

D Expense Reduction — Investors Bank & Trust Company (IBT) serves as custodian of the Portfolio. Pursuant to the custodian agreement, IBT receives a fee reduced by credits which are determined based on the average daily cash balance the Portfolio maintains with IBT. All credit balances used to reduce the Portfolio's custodian fees are reported as a reduction of expenses in the Statement of Operations.

Tax-Managed Mid-Cap Core Portfolio as of April 30, 2007

NOTES TO FINANCIAL STATEMENTS (Unaudited) CONT'D

E Financial Futures Contract — Upon entering a financial futures contract, the Portfolio is required to deposit either in cash or securities an amount (initial margin) equal to a certain percentage of the purchase price indicated in the financial futures contract. Subsequent payments are made or received by the Portfolio (margin maintenance) each day, dependent on daily fluctuations in the value of the underlying security, and are recorded for book purposes as unrealized gains or losses by the Portfolio. The Portfolio's investment in financial futures contracts is designed to hedge against anticipated future changes in price of current or anticipated Portfolio positions. Should prices move unexpectedly, the Portfolio may not achieve the anticipated benefits of the financi al futures contracts and may realize a loss.

F Purchased Options — Upon the purchase of a call or put option, the premium paid by the Portfolio is included in the Statement of Assets and Liabilities as an investment. The amount of the investment is subsequently marked-to-market to reflect the current market value of the option purchased, in accordance with the Portfolio's policies on investment valuations discussed above. If an option which the Portfolio has purchased expires on the stipulated expiration date, the Portfolio will realize a loss in the amount of the cost of the option. If the Portfolio enters into a closing sale transaction, the Portfolio will realize a gain or loss, depending on whether the sales proceeds from the closing sale transaction are greater or less than the cost of the option. If a Portfoli o exercises a put option, it will realize a gain or loss from the sale of the underlying security, and the proceeds from such sale will be decreased by the premium originally paid. If the Portfolio exercises a call option, the cost of the security which the Portfolio purchases upon exercise will be increased by the premium originally paid.

G Securities Sold Short — The Portfolio may sell individual securities short if it owns at least an equal amount of the security sold short or has at the time of sale a right to obtain securities equivalent in kind and amount to the securities sold and provided that, if such right is conditional, the sale is made upon the same conditions (a covered short sale). The Portfolio may sell short securities representing an index or basket of securities whose constituents the Portfolio holds in whole or in part. A short sale of an index or basket security will be a covered short sale if the underlying index or basket of securities is the same or substantially identical to securities held by the Portfolio.

The seller of a short position generally realizes a profit on the transaction if the price it receives on the short sale exceeds the cost of closing out the position by purchasing securities in the market, but generally realizes a loss if the cost of closing out the short position exceeds the proceeds of the short sale. The exposure to loss on covered short sales (to the extent the value of the security sold short rises instead of falls) is offset by the increase in the value of the underlying security or securities retained. The profit or loss on a covered short sale is also affected by the borrowing cost of any securities borrowed in connection with the short sale (which will vary with market conditions) and use of the proceeds of the short sale. The Portfolio expects normally to close its covered short sales by delivering newly-acquired stock.

Exposure to loss on an index or basket security sold short will not be offset by gains on other securities holdings to the extent that the constituent securities of the index or basket security sold short are not held by the Portfolio. Such losses may be substantial.

H Foreign Currency Translation — Investment valuations, other assets, and liabilities initially expressed in foreign currencies are converted each business day into U.S. dollars based upon current exchange rates. Purchases and sales of foreign investment securities and income and expenses are converted into U.S. dollars based upon currency exchange rates prevailing on the respective dates of such transactions. Recognized gains or losses on investment transactions attributable to changes in foreign currency exchange rates are recorded for financial statement purposes as net realized gains and losses on investments. That portion of unrealized gains and losses on investments that results from fluctuations in foreign currency exchange rates is not separately disclosed.

I Use of Estimates — The preparation of the financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements and the reported amounts of income and expense during the reporting period. Actual results could differ from those estimates.

J Other — Investment transactions are accounted for on the date the securities are purchased or sold. Realized gains and losses on securities sold are determined on the basis of identified cost.

K Indemnifications — Under the Portfolio's organizational documents, its officers and Trustees may be indemnified against certain liabilities and expenses arising

Tax-Managed Mid-Cap Core Portfolio as of April 30, 2007

NOTES TO FINANCIAL STATEMENTS (Unaudited) CONT'D

out of the performance of their duties to the Portfolio. Interestholders in the Portfolio are jointly and severally liable for the liabilities and obligations of the Portfolio in the event that the Portfolio fails to satisfy such liabilities and obligations; provided, however, that, to the extent assets are available in the Portfolio, the Portfolio may, under certain circumstances, indemnify interestholders from and against any claim or liability to which such holder may become subject by reason of being or having been an interestholder in the Portfolio. Additionally, in the normal course of business, the Portfolio enters into agreements with service providers that may contain indemnification clauses. The Portfolio's maximum exposure under these arrangements is unknown as this would involve future claims that may be made against the Portfolio that have not yet occurred.

L Interim Financial Statements — The interim financial statements relating to April 30, 2007 and for the six months then ended have not been audited by an independent registered public accounting firm, but in the opinion of the Portfolio's management reflect all adjustments, consisting only of normal recurring adjustments, necessary for the fair presentation of the financial statements.

2 Investment Adviser Fee and Other Transactions with Affiliates

The investment adviser fee is earned by Boston Management and Research (BMR), a wholly-owned subsidiary of EVM, as compensation for management and investment advisory services rendered to the Portfolio. Under the advisory agreement, BMR receives a monthly advisory fee equal to 0.80% annually of the average daily net assets of the Portfolio up to $500 million, and at reduced rates as daily net assets exceed that level. For the six months ended April 30, 2007, the advisory fee amounted to $404,807. Pursuant to a sub-advisory agreement, BMR has delegated the investment management of the Portfolio to Atlanta Capital. BMR pays Atlanta Capital a monthly fee for sub-advisory services provided to the Portfolio equal to 0.55% annually of the average daily net assets up to $500 million, and at reduced rates as daily net assets exceed that level. BMR and Atlanta Capital have agreed to reduce their respective investment advisory fee by an a mount equal to that portion of commissions paid to broker dealers in execution of Portfolio transactions that is consideration for third-party research services. For the six months ended April 30, 2007, BMR waived $988 of its advisory fee. Atlanta Capital, in return, waived $988 of its advisory fee. Except for Trustees of the Portfolio who are not members of EVM's or BMR's organization, officers and Trustees receive remuneration for their services to the Portfolio out of the investment adviser fee and sub-adviser fees. Trustees of the Portfolio who are not affiliated with BMR may elect to defer receipt of all or a percentage of their annual fees in accordance with the terms of the Trustees Deferred Compensation Plan. For the six months ended April 30, 2007, no significant amounts have been deferred.

Certain officers and Trustees of the Portfolio are officers of the above organizations.

3 Investment Transactions

Purchases and sales of investments, other than short-term obligations, aggregated $14,905,763 and $17,420,119, respectively, for the six months ended April 30, 2007.

4 Federal Income Tax Basis of Unrealized Appreciation (Depreciation)

The cost and unrealized appreciation (depreciation) in value of the investments owned at April 30, 2007, as determined on a federal income tax basis, were as follows:

Aggregate cost	$	76,287,361
Gross unrealized appreciation	$	28,243,712
Gross unrealized depreciation		(167,711	)
Net unrealized appreciation	$	28,076,001

5 Financial Instruments

The Portfolio may trade in financial instruments with off-balance sheet risk in the normal course of its investing activities to assist in managing exposure to various market risks. These financial instruments include written options and financial futures contracts and may involve, to a varying degree, elements of risk in excess of the amounts recognized for financial statement purposes.

The notional or contractual amounts of these instruments represent the investment the Portfolio has in particular classes of financial instruments and does not necessarily represent the amounts potentially subject to risk. The measurement of the risks associated with these instruments is meaningful only when all related and offsetting transactions are considered. The Portfolio did not have any open obligations under these financial instruments at April 30, 2007.

Tax-Managed Mid-Cap Core Portfolio as of April 30, 2007

NOTES TO FINANCIAL STATEMENTS (Unaudited) CONT'D

6 Line of Credit

The Portfolio participates with other portfolios and funds managed by BMR and EVM and its affiliates in a $150 million unsecured line of credit agreement with a group of banks. Borrowings will be made by the Portfolio solely to facilitate the handling of unusual and/or unanticipated short-term cash requirements. Interest is charged to each participating portfolio or fund based on its borrowings at an amount above either the Eurodollar rate or Federal Funds rate. In addition, a fee computed at an annual rate of 0.10% on the daily unused portion of the line of credit is allocated among the participating portfolios and funds at the end of each quarter. The Portfolio did not have any significant borrowings or allocated fees for the six months ended April 30, 2007.

7 Recently Issued Accounting Pronouncements

In June 2006, the Financial Accounting Standards Board (FASB) issued FASB Interpretation No. 48, (FIN 48) "Accounting for Uncertainty in Income Taxes – an interpretation of FASB Statement No. 109". FIN 48 clarifies the accounting for uncertainty in income taxes recognized in accordance with FASB Statement No. 109, "Accounting for Income Taxes." This interpretation prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. It also provides guidance on de-recognition, classification, interest and penalties, accounting in interim periods, disclosure and transition. FIN 48 is effective for the first required financial reporting period for fiscal years beginning after December 15, 2006. Management is currently evaluating the impact of applying the various provisions of FIN 48.

In September 2006, the FASB issued Statement of Financial Accounting Standards No. 157, (FAS 157) "Fair Value Measurements". FAS 157 defines fair value, establishes a framework for measuring fair value in accordance with generally accepted accounting principles and expands disclosure about fair value measurements. FAS 157 is effective for fiscal years beginning after November 15, 2007. Management is currently evaluating the impact the adoption of FAS 157 will have on the Portfolio's financial statement disclosures.

Eaton Vance Tax-Managed Mid-Cap Core Fund

BOARD OF TRUSTEES' ANNUAL APPROVAL OF THE INVESTMENT ADVISORY AGREEMENTS

Overview of the Contract Review Process

The Investment Company Act of 1940, as amended (the "1940 Act"), provides, in substance, that each investment advisory agreement between a fund and its investment adviser will continue in effect from year to year only if its continuance is approved at least annually by the fund's board of trustees, including by a vote of a majority of the trustees who are not "interested persons" of the fund ("Independent Trustees"), cast in person at a meeting called for the purpose of considering such approval.

At a meeting of the Boards of Trustees (each a "Board") of the Eaton Vance group of mutual funds (the "Eaton Vance Funds") held on April 23, 2007, the Board, including a majority of the Independent Trustees, voted to approve continuation of existing advisory and sub-advisory agreements for the Eaton Vance Funds for an additional one-year period. In voting its approval, the Board relied upon the affirmative recommendation of the Special Committee of the Board, which is a committee comprised exclusively of Independent Trustees. Prior to making its recommendation, the Special Committee reviewed information furnished for a series of meetings of the Special Committee held in February, March and April 2007. Such information included, among other things, the following:

Information about Fees, Performance and Expenses

• An independent report comparing the advisory and related fees paid by each fund with fees paid by comparable funds;

• An independent report comparing each fund's total expense ratio and its components to comparable funds;

• An independent report comparing the investment performance of each fund to the investment performance of comparable funds over various time periods;

• Data regarding investment performance in comparison to relevant peer groups of funds and appropriate indices;

• Comparative information concerning fees charged by each adviser for managing other mutual funds and institutional accounts using investment strategies and techniques similar to those used in managing the fund;

• Profitability analyses for each adviser with respect to each fund;

Information about Portfolio Management

• Descriptions of the investment management services provided to each fund, including the investment strategies and processes employed;

• Information concerning the allocation of brokerage and the benefits received by each adviser as a result of brokerage allocation, including information concerning the acquisition of research through "soft dollar" benefits received in connection with the funds' brokerage, and the implementation of a soft dollar reimbursement program established with respect to the funds;

• Data relating to portfolio turnover rates of each fund;

• The procedures and processes used to determine the fair value of fund assets and actions taken to monitor and test the effectiveness of such procedures and processes;

Information about each Adviser

• Reports detailing the financial results and condition of each adviser;

• Descriptions of the qualifications, education and experience of the individual investment professionals whose responsibilities include portfolio management and investment research for the funds, and information relating to their compensation and responsibilities with respect to managing other mutual funds and investment accounts;

• Copies of the Codes of Ethics of each adviser and its affiliates, together with information relating to compliance with and the administration of such codes;

• Copies of or descriptions of each adviser's proxy voting policies and procedures;

• Information concerning the resources devoted to compliance efforts undertaken by each adviser and its affiliates on behalf of the funds (including descriptions of various compliance programs) and their record of compliance with investment policies and restrictions, including policies with respect to market-timing, late trading and selective portfolio disclosure, and with policies on personal securities transactions;

• Descriptions of the business continuity and disaster recovery plans of each adviser and its affiliates;

Other Relevant Information

• Information concerning the nature, cost and character of the administrative and other non-investment management services provided by Eaton Vance Management and its affiliates;

• Information concerning management of the relationship with the custodian, subcustodians and fund accountants by each adviser or the funds' administrator; and

• The terms of each advisory agreement.

Eaton Vance Tax-Managed Mid-Cap Core Fund

BOARD OF TRUSTEES' ANNUAL APPROVAL OF THE INVESTMENT ADVISORY AGREEMENTS _CONT'D

In addition to the information identified above, the Special Committee considered information provided from time to time by each adviser throughout the year at meetings of the Board and its committees. Over the course of the twelve-month period ended April 30, 2007, the Board met ten times and the Special Committee, the Audit Committee and the Governance Committee, each of which is a Committee comprised solely of Independent Trustees, met twelve, fourteen and eight times, respectively. At such meetings, the Trustees received, among other things, presentations by the portfolio managers and other investment professionals of each adviser relating to the investment performance of each fund and the investment strategies used in pursuing the fund's investment objective.

For funds that invest through one or more underlying portfolios, the Board considered similar information about the portfolio(s) when considering the approval of advisory agreements. In addition, in cases where the fund's investment adviser has engaged a sub-adviser, the Board considered similar information about the sub-adviser when considering the approval of any sub-advisory agreement.

The Special Committee was assisted throughout the contract review process by Goodwin Procter LLP, legal counsel for the Independent Trustees. The members of the Special Committee relied upon the advice of such counsel and their own business judgment in determining the material factors to be considered in evaluating each advisory and sub-advisory agreement and the weight to be given to each such factor. The conclusions reached with respect to each advisory and sub-advisory agreement were based on a comprehensive evaluation of all the information provided and not any single factor. Moreover, each member of the Special Committee may have placed varying emphasis on particular factors in reaching conclusions with respect to each advisory and sub-advisory agreement.

Results of the Process

Based on its consideration of the foregoing, and such other information as it deemed relevant, including the factors and conclusions described below, the Special Committee concluded that the continuance of the investment advisory agreement of the Tax-Managed Mid-Cap Core Portfolio (the "Portfolio"), the portfolio in which the Eaton Vance Tax-Managed Mid-Cap Core Fund (the "Fund") invests, with Boston Management and Research (the "Adviser"), and the sub-advisory agreement with Atlanta Capital Management (the "Sub-adviser"), including their fee structures, is in the interests of shareholders and, therefore, the Special Committee recommended to the Board approval of the respective agreements. The Board accepted the recommendation of the Special Committee as well as the factors considered and conclusions reached by the Special Committee with respect to the agreements. Accordingly, the Board, including a majority of the Independent T rustees, voted to approve continuation of the investment advisory agreement and the sub-advisory agreement for the Portfolio.

Nature, Extent and Quality of Services

In considering whether to approve the investment advisory agreement and sub-advisory agreements of the Portfolio, the Board evaluated the nature, extent and quality of services provided to the Portfolio by the Adviser and the Sub-adviser.

The Board considered the Adviser's and the Sub-adviser's management capabilities and investment process with respect to the types of investments held by the Portfolio, including the education, experience and number of its investment professionals and other personnel who provide portfolio management, investment research, and similar services to the Portfolio and whose responsibilities include supervising the Sub-adviser. The Board specifically noted the Adviser's in-house equity research capabilities. The Board also took into account the resources dedicated to portfolio management and other services, including the compensation paid to recruit and retain investment personnel, and the time and attention devoted to the Portfolio by senior management. With respect to the Sub-adviser, the Board took into account the resources available to the Sub-adviser in fulfilling its duties under the sub-advisory agreement and the Sub-adviser's e xperience in managing equity portfolios.

The Board reviewed the compliance programs of the Adviser and relevant affiliates thereof, including the Sub-adviser. Among other matters, the Board considered compliance and reporting matters relating to personal trading by investment personnel, selective disclosure of portfolio holdings, late trading, frequent trading, portfolio valuation, business continuity and the allocation of investment opportunities. The Board also evaluated the responses of the Adviser and its affiliates to requests from regulatory authorities such as the Securities and Exchange Commission and the National Association of Securities Dealers.

The Board considered shareholder and other administrative services provided or managed by Eaton Vance Management and its affiliates, including transfer agency and accounting services. The Board evaluated the benefits to shareholders of investing in a fund that is a part of a large family of funds, including the ability, in many cases, to exchange an investment among different funds without incurring additional sales charges.

After consideration of the foregoing factors, among others, the Board concluded that the nature, extent and quality of services provided by the Adviser and Sub-adviser, taken as a whole, are appropriate and consistent with the terms of the investment advisory agreement and sub-advisory agreement, respectively.

Eaton Vance Tax-Managed Mid-Cap Core Fund

BOARD OF TRUSTEES' ANNUAL APPROVAL OF THE INVESTMENT ADVISORY AGREEMENTS _CONT'D

Fund Performance

The Board compared the Fund's investment performance to a relevant universe of similarly managed funds identified by an independent data provider and appropriate benchmark indices. The Board reviewed comparative performance data for the one- and three- year periods ended September 30, 2006 for the Fund. The Board noted that action was taken during 2006 to improve the performance of the Fund and concluded that such actions were effective.

Management Fees and Expenses

The Board reviewed contractual investment advisory fee rates, including any administrative fee rates, payable by the Portfolio and the Fund (referred to collectively as "management fees"). As part of its review, the Board considered the management fees (including administrative fees) and the Fund's total expense ratio for the one-year period ended September 30, 2006, as compared to a group of similarly managed funds selected by an independent data provider. The Board considered the fact that the Adviser waived fees and/or paid expenses for the Fund and had agreed to waive fees and/or pay expenses in an additional amount for the next three years.

After reviewing the foregoing information, and in light of the nature, extent and quality of the services provided by the Adviser, the Board concluded that the management fees charged for advisory and related services and the Fund's total expense ratio are reasonable.

Profitability

The Board reviewed the level of profits realized by the Adviser and relevant affiliates thereof, including the Sub-adviser, in providing investment advisory and administrative services to the Portfolio, the Fund and to all Eaton Vance Funds as a group. The Board considered the level of profits realized without regard to revenue sharing or other payments by the Adviser and its affiliates to third parties in respect of distribution services. The Board also considered other direct or indirect benefits received by the Adviser and its affiliates in connection with its relationship with the Portfolio and the Fund, including the benefits of research services that may be available to the Adviser or Sub-adviser as a result of securities transactions effected for the Portfolio and other advisory clients.

The Board concluded that, in light of the foregoing factors and the nature, extent and quality of the services rendered, the profits realized by the Adviser and its affiliates, including the Sub-adviser, are reasonable.

Economies of Scale

In reviewing management fees and profitability, the Board also considered the extent to which the Adviser and its affiliates, on the one hand, and the Fund, on the other hand, can expect to realize benefits from economies of scale as the assets of the Fund and the Portfolio increase. The Board acknowledged the difficulty in accurately measuring the benefits resulting from the economies of scale with respect to the management of any specific fund or group of funds. The Board reviewed data summarizing the increases and decreases in the assets of the Fund and of all Eaton Vance Funds as a group over various time periods, and evaluated the extent to which the total expense ratio of the Fund and the profitability of the Adviser and its affiliates may have been affected by such increases or decreases. Based upon the foregoing, the Board concluded that the benefits from economies of scale are currently being shared equitably by the Adv iser and its affiliates and the Fund. The Board also concluded that, assuming reasonably foreseeable increases in the assets of the Portfolio, the structure of the advisory fee, which includes breakpoints at several asset levels, can be expected to cause the Adviser and its affiliates and the Fund to continue to share such benefits equitably.

Eaton Vance Tax-Managed Mid-Cap Core Fund

INVESTMENT MANAGEMENT

Eaton Vance Tax-Managed Mid-Cap Core Fund

Officers Thomas E. Faust Jr. President and Trustee William H. Ahern, Jr. Vice President Cynthia J. Clemson Vice President Christine M. Johnston Vice President Aamer Khan Vice President Thomas H. Luster Vice President Michael R. Mach Vice President Robert B. MacIntosh Vice President Duncan W. Richardson Vice President Walter A. Row, III Vice President Judith A. Saryan Vice President Susan Schiff Vice President Thomas Seto Vice President David M. Stein Vice President Mark S. Venezia Vice President Barbara E. Campbell Treasurer Alan R. Dynner Secretary Paul M. O'Neil Chief Compliance Officer				Trustees Samuel L. Hayes, III Chairman Benjamin C. Esty Allen R. Freedman James B. Hawkes William H. Park Ronald A. Pearlman Norton H. Reamer Heidi L. Steiger Lynn A. Stout Ralph F. Verni

Eaton Vance Tax-Managed Mid-Cap Core Fund

INVESTMENT MANAGEMENT CONT'D

Tax-Managed Mid-Cap Core Portfolio

Officers James B. Hawkes President and Trustee William O. Bell, IV Vice President and Co-Portfolio Manager Thomas E. Faust Jr. Vice President and Trustee William R. Hackney, III Vice President and Co-Portfoli o Manager Marilyn Robinson Irvin Vice President and Co-Portfolio Manager Michelle A. Green Treasurer Alan R. Dynner Secretary Paul M. O'Neil Chief Compliance Officer				Trustees Samuel L. Hayes, III Chairman Benjamin C. Esty Allen R. Freedman William H. Park Ronald A. Pearlman Norton H. Reamer Heidi L. Steiger Lynn A. Stout Ralph F. Verni

This Page Intentionally Left Blank

Investment Adviser of Tax-Managed Mid-Cap Core Portfolio
Boston Management and Research

The Eaton Vance Building

255 State Street

Boston, MA 02109

Sub-Adviser of Tax-Managed Mid-Cap Core Portfolio
Atlanta Capital Management Company L.L.C.

1349 West Peachtree Street

Suite 1600

Atlanta, GA 30309

Administrator of Eaton Vance Tax-Managed Mid-Cap Core Fund
Eaton Vance Management

The Eaton Vance Building

255 State Street

Boston, MA 02109

Principal Underwriter
Eaton Vance Distributors, Inc.

The Eaton Vance Building

255 State Street

Boston, MA 02109

(617) 482-8260

Custodian
Investors Bank & Trust Company

200 Clarendon Street

Boston, MA 02116

Transfer Agent
PFPC Inc.

Attn: Eaton Vance Funds

P.O. Box 9653

Providence, RI 02940-9653

(800) 262-1122

Eaton Vance Tax-Managed Mid-Cap Core Fund

The Eaton Vance Building

255 State Street

Boston, MA 02109

This report must be preceded or accompanied by a current prospectus. Before investing, investors should consider carefully the Fund's investment
objective, risks, and charges and expenses. The Fund's current prospectus contains this and other information about the Fund and is available
through your financial advisor. Please read the prospectus carefully before you invest or send money. For further information please call 1-800-225-6265.

1301-6/07 TMMCCSRC

Item 2. Code of Ethics

The registrant has adopted a code of ethics applicable to its Principal Executive Officer, Principal Financial Officer and Principal Accounting Officer. The registrant undertakes to provide a copy of such code of ethics to any person upon request, without charge, by calling 1-800-262-1122.

Item 3. Audit Committee Financial Expert

The registrant’s Board has designated William H. Park, Samuel L. Hayes, III and Norton H. Reamer, each an independent trustee, as its audit committee financial experts. Mr. Park is a certified public accountant who is the Vice Chairman of Commercial Industrial Finance Corp (specialty finance company). Previously, he served as President and Chief Executive Officer of Prizm Capital Management, LLC (investment management firm) and as Executive Vice President and Chief Financial Officer of United Asset Management Corporation (“UAM”) (a holding company owning institutional investment management firms). Mr. Hayes is the Jacob H. Schiff Professor of Investment Banking Emeritus of the Harvard University Graduate School of Business Administration. Mr. Reamer is the President, Chief Executive Officer and a Director of Asset Management Finance Corp. (a specialty finance company serving the investment management industry) and is President of Unicorn Corporation (an investment and financial advisory services company). Formerly, Mr. Reamer was Chairman and Chief Operating Officer of Hellman, Jordan Management Co., Inc. (an investment management company) and Advisory Director of Berkshire Capital Corporation (an investment banking firm), Chairman of the Board of UAM and Chairman, President and Director of the UAM Funds (mutual funds).

Item 4. Principal Accountant Fees and Services

Not required in this filing

Item 5. Audit Committee of Listed registrants

Not required in this filing.

Item 6. Schedule of Investments

Please see schedule of investments contained in the Report to Stockholders included under Item 1 of this Form N-CSR.

Item 7. Disclosure of Proxy Voting Policies and Procedures for Closed-End Management Investment Companies

Not required in this filing.

Item 8. Portfolio Managers of Closed-End Management Investment Companies

Not required in this filing.

Item 9. Purchases of Equity Securities by Closed-End Management Investment Company and Affiliated Purchasers.

Not required in this filing.

Item 10. Submission of Matters to a Vote of Security Holders.

No Material Changes.

Item 11. Controls and Procedures

(a) It is the conclusion of the registrant’s principal executive officer and principal financial officer that the effectiveness of the registrant’s current disclosure controls and procedures (such disclosure controls and procedures having been evaluated within 90 days of the date of this filing) provide reasonable assurance that the information required to be disclosed by the registrant has been recorded, processed, summarized and reported within the time period specified in the Commission’s rules and forms and that the information required to be disclosed by the registrant has been accumulated and communicated to the registrant’s principal executive officer and principal financial officer in order to allow timely decisions regarding required disclosure.

(b) There have been no changes in the registrant’s internal controls over financial reporting during the second fiscal quarter of the period covered by this report that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting.

Item 12. Exhibits

(a)(1)		Registrant’s Code of Ethics – Not applicable (please see Item 2).
(a)(2)(i)		Treasurer’s Section 302 certification.
(a)(2)(ii)		President’s Section 302 certification.
(b)		Combined Section 906 certification.

Signatures

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Tax-Managed Mid-Cap Core Portfolio

By:	/s/ James B. Hawkes
	James B. Hawkes
	President

June 12, 2007

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated.

By:	/s/ Barbara E. Campbell
	Barbara E. Campbell
	Assistant Treasurer

June 12, 2007

By:	/s/ James B. Hawkes
	James B. Hawkes
	President

June 12, 2007

EX-99.CERT 2 a07-16853_2ex99dcert.htm EX-99.CERT

Exhibit 99.CERT

Tax-Managed Mid-Cap Core Portfolio

FORM N-CSR

Exhibit 11(a)(2)(i)

CERTIFICATION

I, Barbara E. Campbell; certify that:

1. I have reviewed this report on Form N-CSR of Tax-Managed Mid-Cap Core Portfolio;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations, changes in net assets, and cash flows (if the financial statements are required to include a statement of cash flows) of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Rule 30a-3(c) under the Investment Company Act of 1940) and internal control over financial reporting (as defined in Rule 30a-3(d) under the Investment Company Act of 1940) for the registrant and have:

(a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

(b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

(c) Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of a date within 90 days prior to the filing date of this report based on such evaluation; and

(d) Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s second fiscal quarter of the period covered by this report that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer(s) and I have disclosed to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

(a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize, and report financial information; and

(b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

June 12, 2007

	/s/ Barbara E. Campbell
	Barbara E. Campbell
	Assistant Treasurer

Tax-Managed Mid-Cap Core Portfolio

FORM N-CSR

Exhibit 11(a)(2)(ii)

CERTIFICATION

I, James B. Hawkes; certify that:

1. I have reviewed this report on Form N-CSR of Tax-Managed Mid-Cap Core Portfolio;

(b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

June 12, 2007

	/s/ James B. Hawkes
	James B. Hawkes
	President

EX-99.906CERT 3 a07-16853_2ex99d906cert.htm EX-99.906CERT

Exhibit 99.906CERT

Form N-CSR Item 11(b) Exhibit

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

The undersigned hereby certify in their capacity as Treasurer and President, respectively, of Tax-Managed Mid-Cap Core Portfolio (the “Portfolio”) that:

(a) the Semi-Annual Report of the Portfolio on Form N-CSR for the period ended April 30, 2007 (the “Report”) fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended; and

(b) the information contained in the Report fairly presents, in all material respects, the financial condition and the results of operations of the Portfolio f or such period.

A signed original of this written statement required by section 906 has been provided to the Portfolio and will be retained by the Portfolio and furnished to the Securities and Exchange Commission or its staff upon request.

Tax-Managed Mid-Cap Core Portfolio

June 12, 2007

/s/ Barbara E. Campbell
Barbara E. Campbell
Assistant Treasurer

June 12, 2007

/s/ James B. Hawkes
James B. Hawkes
President

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