Exhibit 99.1

Catamaran Corporation Announces Strong First Quarter Financial Results

-Revenue of $3.2 billion increases 88% versus Q1 2012-

-Record Quarterly Net Income of $51.4 million-

Lisle, Illinois, May 2, 2013 - Catamaran Corporation (“Catamaran” or the “Company”) (NASDAQ: CTRX, TSX: CCT), a leading provider of pharmacy benefit management (“PBM”) services and technology, announces its financial results for the three month period ended March 31, 2013.

Q1 2013 Highlights

• Revenue increased 88% on a year over year basis to $3.2 billion in Q1 2013, compared to $1.7 billion in Q1 2012

• Gross profit increased 125% to $248.4 million in Q1 2013, compared to $110.4 million in Q1 2012

• EBITDA¹ increased 164% to $143.5 million in Q1 2013, compared to $54.4 million in Q1 2012

• Net income attributable to the Company of $51.4 million, or $0.25 per share (fully-diluted) in Q1 2013, compared to $26.3 million, or $0.21 per share (fully-diluted) in Q1 2012

• Adjusted EPS¹ (fully-diluted) increased 62% to $0.42 in Q1 2013, compared to $0.26 in Q1 2012

• Cash flow from operations increased 13% to $63.3 million in Q1 2013, compared to $56.2 million in Q1 2012

• The Company repaid $100 million of debt in Q1 2013

• Adjusted prescription claim volume¹ for the PBM segment increased 93% to 66.4 million in Q1 2013, compared to 34.4 million in Q1 2012

• Generic dispense rate increased to an industry leading 83% for Q1 2013, compared to 80% in Q1 2012

• Successfully converted one HCIT client to PBM services in the quarter

• The Company's specialty brand, BriovaRx™, has been awarded the Specialty Pharmacy Accreditation from URAC, a Washington, D.C.-based accrediting organization that establishes quality standards for the healthcare industry

“Building on the transformative events of 2012, Catamaran had a very strong start to 2013. We continued the full scale integration of Catalyst into our operations during the quarter. In the midst of our integration, we remained focused on executing against our operating plan by delivering another successful implementation season. The Catamaran brand and our distinct product offerings continued to resonate in the market as evidenced by increased proposal requests, across every market we serve. Catamaran is off to a great start in 2013, and we expect to continue to deliver strong results for the remainder of the year and continued growth going forward," said Mark Thierer, Chairman and CEO of Catamaran Corporation.

Financial Review

Revenue and Gross Profit segmented by PBM and HCIT:

Catamaran evaluates segment performance based on revenue and gross profit. Reconciliations of the Company's business segments, PBM and Health Care Information Technology (“HCIT”), to the consolidated financial statements for the three month periods ended March 31, 2013 and 2012 are as follows:

Three months ended March 31, (unaudited, in thousands)

	PBM						HCIT						Consolidated
	2013			2012			2013			2012			2013			2012
Revenue	$	3,181,553		$	1,681,145		$	38,163		$	35,952		$	3,219,716		$	1,717,097
Cost of revenue	2,954,101			1,590,189			17,243			16,519			2,971,344			1,606,708
Gross profit	$	227,452		$	90,956		$	20,920		$	19,433		$	248,372		$	110,389
Gross profit %	7.1		%	5.4		%	54.8		%	54.1		%	7.7		%	6.4		%

PBM Revenue

Q1 2013 PBM revenue increased $1.5 billion, or 89%, to $3.2 billion, compared to $1.7 billion in Q1 2012. The increase in

revenue is primarily due to the recent merger with Catalyst, which was completed on July 2, 2012, as well as increased prescription claim volume as a result of implementation of new customer contracts in 2013.

HCIT Revenue

HCIT revenue increased $2.2 million, or 6%, to $38.2 million in Q1 2013 compared to $36.0 million in Q1 2012. The increase was primarily due to an increase in revenues earned from transaction processing and revenues generated from the HCIT customer base acquired from Catalyst.

Consolidated Gross Profit

Gross profit for Q1 2013 increased $138.0 million, or 125%, to $248.4 million compared to $110.4 million in Q1 2012. The increase is due to incremental PBM revenues generated from the recent merger with Catalyst and new customer implementations in 2013. The gross profit percentage increased to 7.7% of revenue in Q1 2013 from 6.4% of revenue in Q1 2012. The gross profit percentage increased primarily as a result of synergies realized from the integrations of Catalyst customers as well as higher utilization of generics and specialty medications.

Selling, General and Administrative (“SG&A”) Costs

SG&A costs for Q1 2013 increased $43.8 million, or 77%, to $100.5 million compared to $56.7 million in Q1 2012. SG&A costs consist primarily of employee costs in addition to professional services costs, facilities and costs not related to cost of revenue.

SG&A costs increased due to the addition of operating costs related to the Company's merger with Catalyst, as well as additional resources added to support the overall growth of the Company.

Amortization

Total amortization of intangible assets for Q1 2013 and Q1 2012 was $50.1 million and $10.3 million, respectively, an increase of $39.7 million. The increase in expense was driven primarily by the amortization of the intangible asset acquired in the merger with Catalyst.

Interest Expense

Interest expense for Q1 2013 was $11.0 million compared to $1.2 million in Q1 2012. The increase is primarily due to interest expense related to the Company's credit facility entered into in connection with the merger with Catalyst.

Income Taxes

The Company recognized income tax expense of $23.0 million for Q1 2013, representing an effective tax rate of 29%, compared to $13.4 million, or 34%, for the same period in 2012. The increase in income tax expense was mainly due to higher taxable income during the current quarter as compared to the prior year. The Company's effective tax rate decreased primarily due to the tax benefits related to cross-jurisdictional financing.

Net Income and EPS attributable to the Company

The Company reported Q1 2013 net income attributable to the Company of $51.4 million, or $0.25 per share (fully-diluted), compared to $26.3 million, or $0.21 per share (fully-diluted), in Q1 2012. Net income attributable to the Company increased during Q1 2013 compared to Q1 2012due to increased revenues and operating income as a result of the recent merger with Catalyst and other new customer implementations during 2013. The increase was partially offset by increases in interest expense and amortization of intangible assets as well as an increase in the common shares of the Company outstanding. Shares increased primarily due to the Company's issuance of approximately 12.0 million common shares in May 2012 in a public offering and the issuance of 66.8 million shares to complete the merger with Catalyst.

Adjusted EPS¹ (fully-diluted), which excludes all amortization of intangible assets of $50.1 million, net of tax, increased 62% to $0.42 per share (fully-diluted) in Q1 2013, compared to $0.26 per share (fully-diluted) in Q1 2012.

EBITDA¹

Q1 2013 EBITDA increased 164% to $143.5 million compared to $54.4 million in Q1 2012. The EBITDA growth was due to additional business generated from the recent merger with Catalyst and the associated synergies, as well as new contract implementations, offset by increased costs due to additional resources added to support the growth of the PBM segment.

Cash Flow

For Q1 2013, the Company generated $63.3 million of cash from operations, compared to $56.2 million of cash during the same period in 2012 mainly due to an increase in net income. Due to strong cash flow from operations in Q1 2013, the Company was able to repay $100 million of debt on its revolving credit facility.

2013 Full Year Financial Guidance

With today's announcement, the Company is re-affirming its 2013 Full Year Financial Guidance.

▪ Revenue of $14.2 to $14.6 billion

▪ EBITDA¹ of $660 to $670 million

▪ GAAP EPS (fully-diluted) of $1.18 to $1.25

▪ Adjusted EPS¹ (fully-diluted) of $1.81 to $1.88 (excluding all amortization of intangible assets)

Notice of Conference Call

Catamaran will host a conference call on Thursday, May 2, 2013, at 8:30 a.m. ET to discuss its financial results. Mark Thierer, Chairman and CEO, and Jeff Park, EVP and CFO, will co-chair the call. This call is being webcast and can be accessed from the IR Events page of the Catamaran Corporation web site at www.catamaranrx.com.  An archived replay of the webcast will be available for 90 days.

¹Non-GAAP Financial Measures

Catamaran reports its financial results in accordance with generally accepted accounting principles in the United States (“GAAP”). Catamaran's management also evaluates and makes operating decisions using various other measures. Two such measures are Adjusted EPS and EBITDA, which are non-GAAP financial measures. Catamaran's management believes that these two measures provide useful supplemental information regarding the performance of Catamaran's business operations.

Adjusted EPS adds back the impact of all intangible assets amortization, net of tax. Amortization of intangible asset arises from the acquisition of intangible assets in connection with the Company's business acquisitions. The Company excludes intangible assets amortization from EPS because it believes: (i) the amount of such expenses in any specific period may not directly correlate to the underlying performance of Catamaran's business operations and; (ii) such expenses can vary significantly between periods as a result of new acquisitions and full amortization of previously acquired intangible assets. Investors should note that the use of these intangible assets contributes to revenue in the periods presented as well as future periods and should also note that such expenses will recur in future periods.

EBITDA is a non-GAAP measure that management believes is a useful supplemental measure of operating performance. EBITDA consists of earnings attributable to the company prior to depreciation, amortization, interest and other expense, net, income taxes and adjustments to remove the applicable impact of any non-controlling interest. Management believes it is useful to exclude these items, as they are essentially, amounts that cannot be influenced by management in the short term.

The 2013 full year EBITDA guidance was computed using the Company's estimated 2013 earnings attributable to the Company prior to depreciation, amortization, interest and other expense, net, income taxes and adjustments to remove the applicable impact of any non-controlling interest. The 2013 full year Adjusted EPS guidance was computed by taking the Company's GAAP EPS (fully-diluted) guidance and adding back the expected impact of all 2013 amortization of intangible assets totaling approximately $195 million, less estimated income taxes.

Adjusted prescription claim volume equals Catamaran's mail service prescriptions multiplied by three, plus its retail and specialty prescriptions. The mail service prescriptions are multiplied by three to adjust for the fact that they typically include approximately three times the amount of product days supplied compared with retail prescriptions.

Management believes that Adjusted EPS, EBITDA and adjusted prescription claim volume provide useful supplemental information to management and investors regarding the performance of the Company's business operations and facilitate comparisons to its historical operating results. Management also uses this information internally for forecasting and budgeting as it believes that the measures are indicative of the Company's core operating results. Note, however, that these items are performance measures only, and do not provide any measure of the Company's cash flow or liquidity. Non-GAAP financial measures should not be considered as a substitute for measures of financial performance in accordance with GAAP, and investors and potential investors are encouraged to review the reconciliations of Adjusted EPS and EBITDA to their most directly comparable GAAP measure.

Adjusted EPS and EBITDA do not have standardized meanings prescribed by GAAP. The Company's method of calculating these items may differ from the methods used by other companies and, accordingly, may not be comparable to similarly titled measures used by other companies.

EBITDA Reconciliation	Three Months Ended March 31,
(in thousands)	2013			2012
	(unaudited)
Net income attributable to the Company (GAAP)	$	51,408		$	26,342
Add:
Depreciation of property and equipment	8,103			3,055
Amortization of intangible assets	50,056			10,318
Interest and other expense, net	11,039			1,240
Income tax expense	23,028			13,419
Adjustments related to non-controlling interest	(92		)	—
EBITDA	$	143,542		$	54,374

Adjusted EPS Reconciliation
(in thousands, except per share data)
	Three Months Ended March 31,
	2013						2012
	Operational Results			Per Diluted Share			Operational Results			Per Diluted Share
	(unaudited)
Net income attributable to the Company (GAAP)	$	51,408		$	0.25		$	26,342		$	0.21
Amortization of intangible assets	50,056			0.24			10,318			0.08
Tax effect of reconciling item	(14,466		)	(0.07		)	(3,477		)	(0.03		)
Non-GAAP net income attributable to the Company	$	86,998		$	0.42		$	33,183		$	0.26

About Catamaran Corporation

Catamaran, one of the industry's fastest-growing pharmacy benefits managers, helps organizations and the communities they serve take control of prescription drug costs. Managing more than 250 million prescriptions each year on behalf of 25 million members, our flexible, holistic solutions improve patient care and empower individuals to take charge of their health. Processing one in every five prescription claims in the U.S., Catamaran's skill and scale deliver compelling financial results and sustainable improvement in the overall health of members. Catamaran is headquartered in Lisle, IL. with multiple locations in the U.S. and Canada. For more information, please visit www.catamaranrx.com.

Forward-Looking Statements

Certain information included herein is forward-looking within the meaning of certain securities laws and is subject to important risks, uncertainties and assumptions. This forward-looking information includes, among other things, information with respect to the Company’s anticipated operating results and the Company's objectives and the strategies to achieve those objectives, as well as information with respect to the Company’s beliefs, plans, expectations, anticipations, estimates and intentions. Forward-looking statements are necessarily based upon a number of estimates and assumptions that, while considered reasonable by management at this time, are inherently subject to significant business, economic and competitive uncertainties and contingencies. We caution that such forward-looking statements involve known and unknown risks, uncertainties and other risks that may cause our actual financial results, performance, or achievements to be materially different from our estimated future results, performance or achievements expressed or implied by those forward-looking statements. Numerous factors could cause actual results to differ materially from those in the forward-looking statements, including without limitation, our dependence on, and ability to retain, key customers; our ability to achieve increased market acceptance for our product offerings and penetrate new markets; consolidation in the healthcare industry; the existence of undetected errors or similar problems in our software products; our ability to identify and complete acquisitions, manage our growth, integrate acquisitions and achieve expected synergies from acquisitions; our ability to compete successfully; potential liability for the use of incorrect or incomplete data; the length of the sales cycle for our solutions and services; interruption of our operations due to outside sources; maintaining our intellectual property rights and litigation involving intellectual property rights; our ability to obtain, use or successfully integrate third-party licensed technology; compliance with existing laws, regulations and industry initiatives and future changes in laws or regulations in the healthcare industry; breach of our security by third parties; our dependence on the expertise of our key personnel; our access to sufficient capital to fund our future requirements; potential write-offs of goodwill or other intangible assets; and the outcome of any legal proceeding that has been or may be instituted against us. This list is not exhaustive of the factors that may affect any of our forward-looking statements and is subject to change.

In addition, numerous factors could cause actual results with respect to the merger with Catalyst Health Solutions, Inc. ("Catalyst" or the "Merger") to differ materially from those in the forward-looking statements, including without limitation, the possibility that the expected efficiencies and cost savings from the Merger will not be realized, or will not be realized within the expected time period; the risk that the Company's and Catalyst's businesses will not be integrated successfully; disruption from the Merger making it more difficult to maintain business and operational relationships; the risk of customer attrition; and the impact on the availability of funds for other business purposes due to our debt service obligations and funds required to integrate Catalyst.

When relying on forward-looking information to make decisions, investors and others should carefully consider the foregoing factors and other uncertainties and potential events. In making the forward-looking statements contained herein, the Company does not assume any significant future acquisitions, dispositions or one-time items. It does assume, however, the renewal of certain customer contracts. Every year, the Company has major customer contracts that come up for renewal. In addition, the Company also assumes new customer contracts. In this regard, the Company is pursuing large opportunities that present a very long and complex sales cycle which substantially affects its forecasting abilities. The Company has assumed certain timing for the realization of these opportunities which it believes is reasonable but which may not be achieved. Furthermore, the pursuit of these larger opportunities does not ensure a linear progression of revenue and earnings since they may involve significant up-front costs followed by renewals and cancellations of existing contracts. The Company has assumed certain revenues which may not be realized. The Company has also assumed that the material factors referred to in the previous paragraphs will not cause such forward-looking information to differ materially from actual results or events. The foregoing list of factors is not exhaustive and is subject to change and there can be no assurance that such assumptions will reflect the actual outcome of such items or factors.Other factors that should be considered are discussed from time to time in Catamaran's filings with the U.S. Securities and Exchange Commission, including the risks and uncertainties discussed under the captions “Risk Factors” and “Management's Discussion and Analysis of Financial Condition and Results of Operations” in our Annual Report on Form 10-K and subsequent Form 10-Qs, which are available at www.sec.gov. Investors are cautioned not to put undue reliance on forward-looking statements. All subsequent written and oral forward-looking statements attributable to Catamaran or persons acting on our behalf are expressly qualified in their entirety by this notice. We disclaim any intent or obligation to update publicly these forward-looking statements, whether as a result of new information, future events or otherwise. 

THE FORWARD-LOOKING INFORMATION CONTAINED IN THIS RELEASE REPRESENTS THE COMPANY’S CURRENT EXPECTATIONS AND, ACCORDINGLY, IS SUBJECT TO CHANGE. HOWEVER, THE COMPANY EXPRESSLY DISCLAIMS ANY INTENTION OR OBLIGATION TO UPDATE OR REVISE ANY FORWARD-LOOKING INFORMATION, WHETHER AS A RESULT OF NEW INFORMATION, FUTURE EVENTS OR OTHERWISE, EXCEPT AS REQUIRED BY APPLICABLE LAW.

For more information, please contact:

Tony Perkins

Investor Relations

Catamaran Corporation    

(312) 261-7805

tony.perkins@catamaranrx.com

CATAMARAN CORPORATION

Consolidated Balance Sheets

(in thousands, except share data)

	March 31, 2013			December 31, 2012
	(unaudited)
ASSETS
Current assets
Cash and cash equivalents	$	311,356		$	370,776
Restricted cash	32,191			52,422
Accounts receivable, net of allowance for doubtful accounts of $6,520 (2012 — $7,899)	727,462			725,809
Rebates receivable	316,866			302,461
Other current assets	111,634			101,311
Total current assets	1,499,509			1,552,779
Property and equipment, net of accumulated depreciation of $72,151 (2012 — $64,048)	123,693			105,201
Goodwill	4,478,318			4,478,038
Other intangible assets, net of accumulated amortization of $210,409 (2012 — $178,188)	1,148,935			1,198,991
Other long-term assets	46,339			50,118
Total assets	$	7,296,794		$	7,385,127
LIABILITIES AND EQUITY
Current liabilities
Accounts payable	$	610,681		$	644,818
Accrued expenses and other current liabilities	250,100			254,811
Pharmacy benefit management rebates payable	292,526			302,065
Current portion - long-term debt	55,000			41,250
Total current liabilities	1,208,307			1,242,944
Deferred income taxes	340,452			344,232
Long-term debt	1,019,880			1,132,153
Other long-term liabilities	51,006			55,937
Total liabilities	2,619,645			2,775,266
Shareholders’ equity
Common shares: no par value, unlimited shares authorized; 205,905,384 shares issued and outstanding, March 31, 2013 (December 31, 2012 — 205,399,102 shares)	4,202,801			4,180,778
Additional paid-in capital	63,864			73,530
Retained earnings	406,399			354,991
Accumulated other comprehensive income	(1,930		)	(2,191		)
Total shareholders' equity	4,671,134			4,607,108
Non-controlling interest	6,015			2,753
Total equity	4,677,149			4,609,861
Total liabilities and equity	$	7,296,794		$	7,385,127

CATAMARAN CORPORATION

Consolidated Statements of Operations

(in thousands, except share and per share data)

	Three Months Ended March 31,
	2013			2012
	(unaudited)
Revenue	$	3,219,716		$	1,717,097
Cost of revenue	2,971,344			1,606,708
Gross profit	248,372			110,389
Expenses:
Selling, general and administrative	100,495			56,714
Depreciation of property and equipment	6,970			2,356
Amortization of intangible assets	50,056			10,318
	157,521			69,388
Operating income	90,851			41,001
Interest and other expense, net	11,039			1,240
Income before income taxes	79,812			39,761
Income tax expense (benefit):
Current	39,680			13,655
Deferred	(16,652		)	(236		)
	23,028			13,419
Net income	$	56,784		$	26,342
Less: Net income attributable to non-controlling interest	5,376			—
Net income attributable to the Company	$	51,408		$	26,342
Earnings per share attributable to the Company:
Basic	$	0.25		$	0.21
Diluted	$	0.25		$	0.21
Weighted average number of shares used in computing earnings per share:
Basic	205,576,875			125,057,366
Diluted	206,423,549			126,568,958

CATAMARAN CORPORATION

Consolidated Statements of Cash Flows

(in thousands)

	Three Months Ended March 31,
	2013			2012
	(unaudited)
Cash flows from operating activities:
Net income	$	56,784		$	26,342
Items not involving cash:
Stock-based compensation	6,644			2,789
Depreciation of property and equipment	8,103			3,055
Amortization of intangible assets	50,056			10,318
Deferred lease inducements and rent	14,528			51
Deferred income taxes	(16,652		)	(236		)
Tax benefit on stock-based compensation plans	(4,928		)	(7,789		)
Amortization of deferred financing fees	2,493			—
Changes in operating assets and liabilities, net of effects from acquisitions:
Accounts receivable	(1,664		)	(31,842		)
Rebates receivable	(14,553		)	(8,777		)
Restricted cash	227			(665		)
Other current assets	12,467			4,429
Accounts payable	(34,136		)	44,729
Accrued expenses and other current liabilities	(10,154		)	7,630
Pharmacy benefit management rebates payable	(8,674		)	7,225
Other	2,764			(1,048		)
Net cash provided by operating activities	63,305			56,211
Cash flows from investing activities:
Proceeds from restricted cash	20,004			—
Acquisition, net of cash acquired	—			(243,178		)
Purchases of property and equipment	(25,243		)	(6,141		)
Net cash used by investing activities	(5,239		)	(249,319		)
Cash flows from financing activities:
Proceeds from issuance of debt	—			100,000
Repayment of debt	(100,000		)	—
Tax benefit on stock-based compensation plans	4,928			7,789
Proceeds from exercise of options	785			3,334
Payments of contingent consideration	(23,203		)	—
Net cash (used) provided by financing activities	(117,490		)	111,123
Effect of foreign exchange on cash balances	4			40
Decrease in cash and cash equivalents	(59,420		)	(81,945		)
Cash and cash equivalents, beginning of period	370,776			341,382
Cash and cash equivalents, end of period	$	311,356		$	259,437