Exhibit 10.1

UNITED THERAPEUTICS CORPORATION

SUPPLEMENTAL EXECUTIVE RETIREMENT PLAN

RABBI TRUST DOCUMENT

This Agreement made this 28^th day of December, 2007, by and between UNITED THERAPEUTICS CORPORATION (hereinafter referred to as the “Company”), a Delaware corporation, and WILMINGTON TRUST COMPANY, a Delaware corporation, as trustee (hereinafter referred to as the “Trustee”);

WHEREAS, Company has adopted the United Therapeutics Corporation Supplemental Executive Retirement Plan (the “Plan”);

WHEREAS, Company has incurred or expects to incur liability under the terms of such Plan with respect to the individuals participating in such Plan;

WHEREAS, Company wishes to establish a trust (hereinafter called “Trust”) and to contribute to the Trust assets that shall be held therein, subject to the claims of Company’s creditors in the event of Company’s Insolvency, as herein defined, until paid to Plan participants and their beneficiaries in such manner and at such times as specified in the Plan;

WHEREAS, it is the intention of the parties that this Trust shall constitute an unfunded arrangement and shall not affect the status of the Plan as an unfunded plan maintained for the purpose of providing deferred compensation for a select group of management or highly compensated employees for purposes of Title I of the Employee Retirement Income Security Act of 1974, as amended;

WHEREAS, it is the intention of Company to make contributions to the Trust to provide itself with a source of funds to assist it in the meeting of its liabilities under the Plan;

NOW, THEREFORE, the parties do hereby establish the Trust and agree that the Trust shall be comprised, held and disposed of as follows:

Section 1. Establishment of Trust

(a) Company hereby deposits with Trustee in trust an amount, which shall become the principal of the Trust to be held, administered and disposed of by Trustee as provided in this Trust Agreement.

(b) The Trust hereby established shall be irrevocable.

(c) The Trust is intended to be a grantor trust, of which Company is the grantor, within the meaning of subpart E, part I subchapter J, chapter 1, subtitle A of the Internal Revenue Code of 1986, as amended, and shall be construed accordingly.

(d) The principal of the Trust, and any earnings thereon, shall be held separate and apart from other funds of Company and shall be used exclusively for the uses and purposes of Plan participants and general creditors as herein set forth. Plan participants and their beneficiaries shall have no preferred claim on, or any beneficial ownership interest in, any assets of the Trust. Any rights created under the Plan and this Trust Agreement shall be mere unsecured contractual rights of Plan participants and their beneficiaries against Company. Any assets held by the Trust will be subject to the claims of Company’s general creditors under federal and state law in the event of Insolvency, as defined in Section 3(a) herein.

(e) Company, in its sole discretion, may at any time, or from time to time, make additional deposits of cash or other property in trust with Trustee to augment the principal to be held, administered and disposed of by Trustee as provided in this Trust Agreement. Neither Trustee nor any Plan participant or beneficiary shall have any right to compel such additional deposits.

(f) Notwithstanding Section 1(e), within 5 days following the occurrence of a Potential Change of Control (as defined herein) or, if earlier, at least 5 days prior to the occurrence of a Change of Control (as defined herein), the Company shall make an irrevocable contribution to the Trust in an amount that is sufficient to pay each Plan participant or beneficiary the benefits to which Plan participants or their beneficiaries would be entitled pursuant to the terms of the Plan as of the date on which the Change of Control occurred.

Section 2. Payments to Plan Participants and Their Beneficiaries

(a) Company shall deliver to Trustee a schedule (the “Payment Schedule”) that indicates the amounts payable in respect of each Plan participant (and his or her beneficiaries), that provides a formula or other instructions acceptable to Trustee for determining the amounts so payable, the form in which such amount is to be paid (as provided for or available under the Plan), and the time of commencement for payment of such amounts. Except as otherwise provided herein, Trustee shall make payments to the Plan participants and their beneficiaries in accordance with the Payment Schedule. Trustee shall make provision for the reporting and withholding of any federal, state or local taxes that may be required to be withheld with respect to the payment of benefits pursuant to the terms of the Plan and shall pay amounts withheld to the appropriate taxing authorities or determine that such amounts have been reported, withheld and paid by Company (see attached fee schedule).

Section 3. Trustee Responsibility Regarding Payments to Trust Beneficiary When Company is Insolvent.

(a) Trustee shall cease payment of benefits to Plan participants and their beneficiaries if the Company is Insolvent. Company shall be considered “Insolvent” for purposes of this Trust Agreement if (i) Company is unable to pay its debts as they become due, or (ii) Company is subject to a pending proceeding as a debtor under the United States Bankruptcy Code.

(b) At all times during the continuance of this Trust, as provided in Section 1(d) hereof, the principal and income of the Trust shall be subject to claims of general creditors of Company under federal and state law as set forth below.

(1) The Board of Directors and the Chief Executive Officer of Company shall have the duty to inform Trustee in writing of Company’s Insolvency. If a person claiming to be a creditor of Company alleges in writing to Trustee that Company has become Insolvent, Trustee shall determine whether company in Insolvent and, pending such determination, Trustee shall discontinue payment of benefits to Plan participants or their beneficiaries.

(2) Unless Trustee has actual knowledge of Company’s Insolvency, or has received notice from Company or a person claiming to be a creditor alleging that Company is Insolvent, Trustee shall have no duty to inquire whether Company is Insolvent. Trustee may in all events rely on such evidence concerning Company’s solvency as may be furnished to Trustee and that provides Trustee with a reasonable basis for making a determination concerning Company’s solvency.

(3) If at any time Trustee has determined that Company is Insolvent, Trustee shall discontinue payments to Plan participants or their beneficiaries and shall hold the assets of the Trust for the benefit of Company’s general creditors. Nothing in this Trust Agreement shall in any way diminish any rights of Plan participants or their beneficiaries to pursue their rights as general creditors of Company with respect to benefits due under the Plan or otherwise.

(4) Trustee shall resume the payment of benefits to Plan participants or their beneficiaries in accordance with Section 2 of this Trust Agreement only after Trustee has determined that Company is not Insolvent (or is no longer Insolvent).

(c) Provided that there are sufficient assets, if Trustee discontinues the payment of benefits from the Trust pursuant to Section 3(b) hereof and subsequently resumes such payments, the first payment following such discontinuance shall include the aggregate amount of all payments due to Plan participants or their beneficiaries under the terms of the Plan for the period of such discontinuance, less the aggregate amount of any payments made to Plan participants or their beneficiaries by Company in lieu of the payments provided for hereunder during any such period of discontinuance.

Section 4. Investment Authority.

(a) Except as otherwise explicitly authorized by this Trust Agreement, the Trust shall be invested in cash, money market accounts, U.S. Treasury obligations, and/or shares of any investment company registered pursuant to the Investment Company Act of 1940 (whether or not the Trustee or any of its affiliates is an advisor to, or other service provider to, such investment company and receives compensation from such investment company for the services provided (which compensation shall be in addition to the compensation of the Trustee under this Trust)). The Company acknowledges that shares in any such investment company are not obligations of the Trustee or any other bank, are not deposits and are not insured by the Federal Deposit Insurance Corporation (the “FDIC”), the Federal Reserve or any other governmental agency. Notwithstanding the foregoing, in no event may Trustee invest in securities (including stock or rights to acquire stock) or obligations issued by Company, other than a de minimis amount held in common investment vehicles in which Trustee invests. All rights associated with assets of the Trust shall be exercised by Trustee or the person designated by Trustee, and shall in no event be exercisable by or rest with Plan participants, except that voting and dividend rights with respect to Trust assets will be exercised by Company.

(b) Company shall have the right, at any time and from time to time, in its sole discretion, to direct Trustee as to the investment and reinvestment of all or specified portions of Trust assets and the income therefrom and to appoint an investment manager or investment managers to direct Trustee as to the investment and reinvestment of all or specified portions thereof. As of the execution of this Trust Agreement, and until Trustee is notified otherwise in writing, Trustee shall be solely responsible for directing the investment and reinvestment of all Trust assets. Notwithstanding any other provision of this Trust Agreement, following a Change of Control of the Company, all of the Trust assets shall be invested in a money market fund selected by the Trustee prior to the consummation of the Change of Control.

(c) The Trustee is specifically authorized to invest idle, or otherwise uninvested cash in the Service class shares of the Wilmington Prime Money Market Portfolio (the “Prime MM Portfolio”), a money market mutual fund managed by an affiliate of the Trustee. Company acknowledges that the Prime MM Portfolio is an entity separate from Wilmington Trust Company; and that shares in the Prime MM Portfolio are not obligations of Wilmington Trust Company, are not deposits and are not insured by the FDIC, the Federal Reserve or any other governmental agency. Wilmington Trust Company or its affiliates are compensated by the Prime MM Portfolio for investment advisory, custodian, shareholder servicing, distribution and other services, and such compensation is described in detail in the prospectus for the Prime MM Portfolio and is in addition to the compensation paid to Trustee hereunder with respect to that portion of the Trust Fund, if any, invested in the Prime MM Portfolio.

(d) Trustee may hold that portion of the Trust Fund as is appropriate, for the ordinary administration and for the disbursement of funds in cash, without liability for interest

notwithstanding Trustee’s receipt of “float” from such uninvested cash, by depositing the same in any bank (including deposits which bear a reasonable rate of interest in a bank or similar financial institution supervised by the United States or a State, even where a bank or financial institution is the Trustee, or is otherwise a fiduciary of the Plan) subject to the rules and regulations governing such deposits, and without regard to the amount of such deposit. In addition, Trustee is specifically authorized to invest idle, or otherwise uninvested, cash in a money market mutual fund selected by Trustee in its sole discretion, including any money market fund associated with Trustee as described in subparagraph (c) above.

Section 5. Disposition of Income

During the term of this Trust, all income received by the Trust, net of expenses and taxes, shall be accumulated and reinvested.

Section 6. Accounting by Trustee

Trustee shall keep accurate and detailed records of all investments, receipts, disbursements, and all other transactions required to be made, including such specific records as shall be agreed upon in writing between Company and Trustee. Within 60 days following the close of each calendar year and within 60 days after the removal or resignation of Trustee, Trustee shall deliver to Company a written account of its administration of the Trust during such year or during the period from the close of the last preceding year to the date of such removal or resignation, setting forth all investments, receipts, disbursements and other transactions effected by it, including a description of all securities and investments purchased and sold with the cost or net proceeds of such purchases or sales (accrued interest paid or receivable being shown separately), and showing all cash, securities and other property held in the Trust at the end of such year or as of the date of such removal or resignation, as the case may be. In addition, Trustee shall provide the Company a monthly statement including such information. Such account statements shall be mailed to Company or, if the Company agrees, delivered via e-mail or other electronic means.

Section 7. Responsibility of Trustee.

(a) Trustee shall act with care, skill, prudence and diligence under the circumstances then prevailing that a prudent person acting in like capacity and familiar with such matters would use in the conduct of any enterprise of a like character and with like aims, provided, however, that Trustee shall incur no liability to any person for any action taken pursuant to a direction, request or approval given by Company or an investment manager which is contemplated by, and in conformity with, the terms of the Plan or this Trust and is given in writing by Company or such investment manager. In the event of a dispute between Company and a party, Trustee may apply to a court of competent jurisdiction to resolve the dispute.

(b) If Trustee undertakes or defends any litigation arising in connection with this Trust, Company agrees to indemnify Trustee against Trustee’s costs, expenses and liabilities (including, without limitation, attorneys’ fees and expenses) relating thereto and to be primarily liable for such payments. If Company does not pay such costs, expenses and liabilities in a reasonably timely manner, Trustee may obtain payment from the Trust. In no event shall Trustee have any liability or responsibility to undertake, defend or continue any litigation unless payment of related fees and expenses is ensured to the reasonable satisfaction of Trustee.

(c) Trustee, at the expense of the Trust or the Company, may consult with legal counsel (who may also be counsel for Company generally) with respect to any of its duties or obligations hereunder provided that Trustee notifies Company in advance (to the extent practicable or if not practicable, as soon as reasonably possible) of incurring such expense.

(d) Trustee, at the expense of the Trust or the Company, may hire agents, accountants, actuaries, investment advisors, financial consultants or other professionals to assist it in performing any of its duties or obligations hereunder.

(e) Trustee shall have, without exclusion, all powers conferred on trustees by applicable law, unless expressly provided otherwise herein, provided, however, that if an insurance policy is held as an asset of the Trust, Trustee shall have no power to name a beneficiary of the policy other than the Trust, to assign the policy (as distinct from conversion of the policy to a different form) other than to a successor Trustee, or to loan to any person the proceeds of any borrowing against such policy.

(f) However, notwithstanding the provisions of Section 7(e) above, Trustee may loan to Company the proceeds of any borrowing against an insurance policy (if any) held as an asset of the Trust.

(g) Notwithstanding any powers granted to Trustee pursuant to this Trust Agreement or to applicable law, Trustee shall not have any power that could give this Trust the objective of carrying on a business and dividing the gains therefrom, within the meaning of section 301.7701-2 of the Procedure and Administrative Regulations promulgated pursuant to the Internal Revenue Code.

(h) Trustee shall have no responsibility or liability respect to: (i) the truth or accuracy of any representation or warranty made in any application or related document provided to the insurer in connection with the issuance or renewal of any insurance policies or insurance contracts, including any representation that the person on whose life an application is being made is eligible to have a contract issued on his or her life; (ii) the selection or monitoring (ongoing or periodic) of any insurance policies or insurance contracts held in the Trust or the insurers issuing such policies or contracts; (iii) the payment of premiums with respect to such policies or contracts; or (iv) the exercise of any rights relating to any such policies or contracts except as directed in writing by Company.

(i) Upon the expiration of one hundred twenty (120) days from the date of Trustee’s annual, quarterly or any other account, the Trustee shall be forever released and discharged from all liability and further accountability to Company or any other person with respect to the accuracy of such accounting and all acts and failures to act of Trustee reflected in such account, except to the extent that Company shall, within such 120-day period, file with Trustee specific written objections to the account. Neither Company, any participant nor any other person shall be entitled to any additional or different accounting by Trustee and Trustee shall not be compelled to file in any court any additional or different accounting. For purposes of regulations promulgated by the FDIC, Trustee’s account statements shall be sufficient information concerning securities transactions effected for the Trust, provided that Company, upon written request, shall have the right to receive at no additional cost written confirmations of such securities transactions, which shall be mailed or otherwise furnished by the Trustee within the timeframe required by applicable regulations.

(j) Trustee shall have no duty or responsibility not expressly set forth in this Trust Agreement. By way of example, but without limiting the matters subject to the foregoing sentence, Trustee shall have no responsibility with respect to the administration or interpretation of the Plan, payment of Plan benefits other than from the assets of the Trust, the calculation of tax to be withheld, reported and/or paid to taxing authorities and (if applicable pursuant to the fee schedule) withholding, remitting, or reporting to taxing authorities of taxes other than from payments made with Trust assets to Plan participants and other than as directed by Company, or maintaining participant records with respect to the Plan.

Section 8. Compensation and Expenses of Trustee.

(a) Company shall pay all administrative and Trustee’s fees and expenses on a monthly basis. If not so paid, the Trustee shall be entitled to deduct such fees and expenses from the Trust.

(b) Company shall indemnify and hold Trustee harmless from and against any and all losses, costs, damages and expenses (including attorney’s fees and disbursements) of any kind or nature (collectively, “Losses”) imposed on or incurred by Trustee by reason of its service pursuant to this Trust Agreement, including any Losses arising out of any threatened, pending or completed claim, action, suit or proceeding, except to the extent such Losses are caused by the gross negligence, willful misconduct or bad faith of Trustee. To the extent not paid by Company, Trustee shall be entitled to deduct such amounts from the Trust.

Section 9. Resignation and Removal of Trustee.

(a) Trustee may resign at any time by written notice to Company, which shall be effective thirty (30) days after receipt of such notice unless Company and Trustee agree otherwise.

(b) Trustee may be removed by Company on thirty (30) days notice or upon shorter notice accepted by Trustee; provided that, following a Change of Control, Trustee may be removed only with the unanimous consent of the participants in the Plan.

(c) If Trustee resigns within three (3) years after a Change of Control, as defined herein, Company shall apply to a court of competent jurisdiction for the appointment of a successor Trustee or for instructions.

(d) Upon resignation or removal of Trustee and appointment of a successor Trustee, all assets shall subsequently be transferred to the successor Trustee. To the extent possible, the transfer shall be completed within thirty (30) days after receipt of notice of resignation, removal or transfer, unless Company extends the time limit.

(e) If Trustee resigns or is removed, a successor shall be appointed, in accordance with Section 10 hereof, by the effective date of resignation or removal under paragraphs (a) or (b) of this section. If no such appointment has been made, Trustee may apply to a court of competent jurisdiction for appointment of a successor or for instructions. All expenses of Trustee in connection with the proceeding shall be allowed as administrative expenses of the Trust.

Section 10. Appointment of Successor.

If Trustee resigns or is removed in accordance with Section 9(a) or (b) hereof, Company may appoint any third party, such as a bank trust department or other party that may be granted corporate trustee powers under state law, as a successor to replace Trustee upon resignation or removal. The appointment shall be effective when accepted in writing by the new Trustee, who shall have all of the rights and powers of the former Trustee, including ownership rights in the Trust assets. The former Trustee shall execute any instrument necessary or reasonably requested by Company or the successor Trustee to evidence the transfer.

Section 11. Amendment or Termination.

(a) This Trust Agreement may be amended by a written instrument executed by Trustee and Company. Notwithstanding the foregoing, no such amendment shall conflict with the terms of the Plan or shall make the Trust revocable. In addition, following a Change of Control, the Trust Agreement may be amended only with the unanimous consent of the participants in the Plan.

(b) The Trust shall not terminate until the date on which Plan participants and their beneficiaries are no longer entitled to benefits pursuant to the terms of the Plan. Upon termination of the Trust any assets remaining in the Trust shall be returned to Company.

Section 12. Miscellaneous.

(a) Any provision of this Trust Agreement prohibited by law shall be ineffective to the extent of any such prohibition, without invalidating the remaining provisions hereof.

(b) Benefits payable to Plan participants and their beneficiaries under this Trust Agreement may not be anticipated, assigned (either at law or in equity), alienated, pledged, encumbered or subjected to attachment, garnishment, levy, execution or other legal or equitable process.

(d) Trustee represents that it qualifies for FDIC prorata worth pass-through insurance coverage in accordance with the standards set forth in applicable federal law and FDIC insurance regulations. If Trustee fails at any time in the future to so qualify for prorata worth pass-through insurance coverage, it will promptly notify Company.

(e) In no event will Trustee have any obligation to provide, and in no event will Trustee provide, any legal, tax, accounting, audit or other advice to Company with respect to the Plan or this Trust. Company acknowledges that it will rely exclusively on the advice of its accountants and/or attorneys with respect to all legal, tax, accounting, audit and other advice required or desired by Company with respect to the Plan or this Trust. Company acknowledges that Trustee has not made any representations of any kind, and will not make any representations of any kind, concerning the legal, tax, accounting, audit or other treatment of the Plan or this Trust.

(f) Company acknowledges that Trustee is not an advisor concerning or a promoter with respect to the Plan or the Trust, but merely is a service provider offering the Trust services expressly set forth in this Agreement. In particular, Company acknowledges that Trustee is not a joint venture or partner with Company’s accountants, auditors, consultants or with any other party, with respect to the Plan or this Trust, and that Trustee and Company’s accountants, auditors and consultants at all times remain independent parties dealing at arm’s length, and independently, with each other and with Company.

(g) Company represents and warrants that the Plan and the administration thereof and the establishment of this Trust comply with applicable law and shall continue to be in compliance therewith.

(h) Trustee shall have no liability for any losses arising out of delays in performing the services which it renders under this Trust Agreement which result from

events beyond its control, including without limitation, interruption of the business of Trustee due to acts of God, acts of governmental authority, acts of war, riots, civil commotions, insurrections, labor difficulties (including, but not limited to, strikes and other work slippages due to slow-downs), or any action of any courier or utility, mechanical or other malfunction, or electronic interruption; provided in each case that Trustee has implemented reasonable procedures or measures to mitigate the effect of such events.

(h) For purposes of this Trust, Change of Control shall mean any transfer of control of the Company by acquisition, merger, hostile takeover or for any other reason whatsoever which also qualifies as a “change in the ownership or effective control of the corporation, or in the ownership of a substantial portion of the assets of the corporation” under Code section 409A(a)(2)(A)(v).:

(i) For purposes of this Trust, a “Potential Change of Control” shall be deemed to have occurred if one of the following events has occurred: (A) the Company enters into an agreement, the consummation of which would result in the occurrence of a Change of Control; (B) the Company or any person publicly announces an intention to take or to consider taking actions which, if consummated, would constitute a Change of Control; or (C) the Board of Directors adopts a resolution to the effect that, for purposes of this Agreement, a Potential Change of Control has occurred.

(j) The Board of Directors of Company as constituted immediately prior to a Potential Change of Control or the consummation of a Change of Control and the Chief Executive Officer of Company shall have the duty to inform Trustee in writing of the occurrence of such Potential Change of Control or Change of Control. Trustee may rely exclusively on this writing and shall have no duty to inquire whether a Potential Change of Control or a Change of Control has taken place or to make any determination as to whether a Potential Change of Control or a Change of Control has occurred or the amount of contribution, if any, required to be made by the Company pursuant to Section 1(f).

Section 13. Effective Date.

The effective date of this Trust Agreement shall be December 28, 2007.

IN WITNESS WHEREOF, the Company and the Trustee have caused this Trust Agreement to be executed and their corporate seals to be attested by their respective duly authorized officers, all as of the day and year first above written.

UNITED THERAPEUTICS CORPORATION

Attest:	/s/ Paul Mahon	By:	/s/ John Ferrari
Corporate Secretary		Name:	John Ferrari
		Title:	Chief Financial Officer and Treasurer

		Address:	1110 Spring Street
			Silver Spring, MD 20910
			Attn: John Ferrari

		Telephone:	301-608-9292
		Telecopier:	301-608-3049

[Corporate Seal]

WILMINGTON TRUST COMPANY, as Trustee

		By:		/s/ Jennifer Matz
		Name:		Jennifer Matz
		Title:		Vice President

		Address:		Rodney Square North
				1100 North Market Street
				Wilmington, DE 19890-0001
				Attn: David Snyder

		Telephone:		302-651-8926
		Telecopier:		302-651-1312