Exhibit 10.5

SUBSIDIARY GUARANTEE

SUBSIDIARY GUARANTEE, dated as of March 31, 2008 (this “ Guarantee ”), made by each of the signatories hereto (together with any other entity that may become a party hereto as provided herein, the “ Guarantors ”), in favor of the purchasers signatory (together with their permitted assigns, the “ Purchasers ”) to that certain Securities Purchase Agreement, dated as of the date hereof, between Advanced Cell Technology, Inc., a Delaware corporation (the “ Company ”) and the Purchasers.

W I T N E S S E T H:

WHEREAS, pursuant to that certain Securities Purchase Agreement, dated as of the date hereof, by and between the Company and the Purchasers (the “ Purchase Agreement ”), the Company has agreed to sell and issue to the Purchasers, and the Purchasers have agreed to purchase from the Company the Debentures, subject to the terms and conditions set forth therein; and

WHEREAS, each Guarantor will directly benefit from the extension of credit to the Company represented by the issuance of the Debentures; and

NOW, THEREFORE, in consideration of the premises and to induce the Purchasers to enter into the Purchase Agreement and to carry out the transactions contemplated thereby, each Guarantor hereby agrees with the Purchasers as follows:

1.              Definitions . Unless otherwise defined herein, terms defined in the Purchase Agreement and used herein shall have the meanings given to them in the Purchase Agreement. The words “hereof,” “herein,” “hereto” and “hereunder” and words of similar import when used in this Guarantee shall refer to this Guarantee as a whole and not to any particular provision of this Guarantee, and Section and Schedule references are to this Guarantee unless otherwise specified. The meanings given to terms defined herein shall be equally applicable to both the singular and plural forms of such terms.  The following terms shall have the following meanings:

“ Guarantee ” means this Subsidiary Guarantee, as the same may be amended, supplemented or otherwise modified from time to time.

“ Obligations ” means, in addition to all other costs and expenses of collection incurred by Purchasers in enforcing any of such Obligations and/or this Guarantee, all of the liabilities and obligations (primary, secondary, direct, contingent, sole, joint or several) due or to become due, or that are now or may be hereafter contracted or acquired, or owing to, of the Company or any Guarantor to the Purchasers, including, without limitation, all obligations under this Guarantee, the Debentures and any other instruments, agreements or other documents executed and/or delivered in connection herewith or therewith, in each case, whether now or hereafter existing, voluntary or involuntary, direct or indirect,

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absolute or contingent, liquidated or unliquidated, whether or not jointly owed with others, and whether or not from time to time decreased or extinguished and later increased, created or incurred, and all or any portion of such obligations or liabilities that are paid, to the extent all or any part of such payment is avoided or recovered directly or indirectly from any of the Purchasers as a preference, fraudulent transfer or otherwise as such obligations may be amended, supplemented, converted, extended or modified from time to time.  Without limiting the generality of the foregoing, the term “Obligations” shall include, without limitation: (i) principal of, and interest on the Debentures and the loans extended pursuant thereto; (ii) any and all other fees, indemnities, costs, obligations and liabilities of the Company or any Guarantor from time to time under or in connection with this Guarantee, the Debentures and any other instruments, agreements or other documents executed and/or delivered in connection herewith or therewith; and (iii) all amounts (including but not limited to post-petition interest) in respect of the foregoing that would be payable but for the fact that the obligations to pay such amounts are unenforceable or not allowable due to the existence of a bankruptcy, reorganization or similar proceeding involving the Company or any Guarantor.

2.              Guarantee .

(a)            Guarantee .

(i)            The Guarantors hereby, jointly and severally, unconditionally and irrevocably, guarantee to the Purchasers and their respective successors, indorsees, transferees and assigns, the prompt and complete payment and performance when due (whether at the stated maturity, by acceleration or otherwise) of the Obligations.

(ii)           Anything herein or in any other Transaction Document to the contrary notwithstanding, the maximum liability of each Guarantor hereunder and under the other Transaction Documents shall in no event exceed the amount which can be guaranteed by such Guarantor under applicable federal and state laws, including laws relating to the insolvency of debtors, fraudulent conveyance or transfer or laws affecting the rights of creditors generally (after giving effect to the right of contribution established in Section 2(b)).

(iii)          Each Guarantor agrees that the Obligations may at any time and from time to time exceed the amount of the liability of such Guarantor hereunder without impairing the guarantee contained in this Section 2 or affecting the rights and remedies of the Purchasers hereunder.

(iv)          The guarantee contained in this Section 2 shall remain in full force and effect until all the Obligations and the obligations of each

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Guarantor under the guarantee contained in this Section 2 shall have been satisfied by indefeasible payment in full.

(v)           No payment made by the Company, any of the Guarantors, any other guarantor or any other Person or received or collected by the Purchasers from the Company, any of the Guarantors, any other guarantor or any other Person by virtue of any action or proceeding or any set-off or appropriation or application at any time or from time to time in reduction of or in payment of the Obligations shall be deemed to modify, reduce, release or otherwise affect the liability of any Guarantor hereunder which shall, notwithstanding any such payment (other than any payment made by such Guarantor in respect of the Obligations or any payment received or collected from such Guarantor in respect of the Obligations), remain liable for the Obligations up to the maximum liability of such Guarantor hereunder until the Obligations are indefeasibly paid in full.

(vi)          Notwithstanding anything to the contrary in this Guarantee, with respect to any defaulted non-monetary Obligations the specific performance of which by the Guarantors is not reasonably possible (e.g. the issuance of the Company’s Common Stock), the Guarantors shall only be liable for making the Purchasers whole on a monetary basis for the Company’s failure to perform such Obligations in accordance with the Transaction Documents.

(b)            Right of Contribution . Subject to Section 2(c), each Guarantor hereby agrees that to the extent that a Guarantor shall have paid more than its proportionate share of any payment made hereunder, such Guarantor shall be entitled to seek and receive contribution from and against any other Guarantor hereunder which has not paid its proportionate share of such payment. Each Guarantor’s right of contribution shall be subject to the terms and conditions of Section 2(c). The provisions of this Section 2(b) shall in no respect limit the obligations and liabilities of any Guarantor to the Purchasers and each Guarantor shall remain liable to the Purchasers for the full amount guaranteed by such Guarantor hereunder.

(c)            No Subrogation .  Notwithstanding any payment made by any Guarantor hereunder or any set-off or application of funds of any Guarantor by the Purchasers, no Guarantor shall be entitled to be subrogated to any of the rights of the Purchasers against the Company or any other Guarantor or any collateral security or guarantee or right of offset held by the Purchasers for the payment of the Obligations, nor shall any Guarantor seek or be entitled to seek any contribution or reimbursement from the Company or any other Guarantor in respect of payments made by such Guarantor hereunder, until all amounts owing to the Purchasers by the Company on account of the Obligations are indefeasibly paid in full. If any amount shall be paid to any Guarantor on account of such

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subrogation rights at any time when all of the Obligations shall not have been paid in full, such amount shall be held by such Guarantor in trust for the Purchasers, segregated from other funds of such Guarantor, and shall, forthwith upon receipt by such Guarantor, be turned over to the Purchasers in the exact form received by such Guarantor (duly indorsed by such Guarantor to the Purchasers, if required), to be applied against the Obligations, whether matured or unmatured, in such order as the Purchasers may determine.

(d)           Amendments, Etc. With Respect to the Obligations . Each Guarantor shall remain obligated hereunder notwithstanding that, without any reservation of rights against any Guarantor and without notice to or further assent by any Guarantor, any demand for payment of any of the Obligations made by the Purchasers may be rescinded by the Purchasers and any of the Obligations continued, and the Obligations, or the liability of any other Person upon or for any part thereof, or any collateral security or guarantee therefor or right of offset with respect thereto, may, from time to time, in whole or in part, be renewed, extended, amended, modified, accelerated, compromised, waived, surrendered or released by the Purchasers, and the Purchase Agreement and the other Transaction Documents and any other documents executed and delivered in connection therewith may be amended, modified, supplemented or terminated, in whole or in part, as the Purchasers may deem advisable from time to time, and any collateral security, guarantee or right of offset at any time held by the Purchasers for the payment of the Obligations may be sold, exchanged, waived, surrendered or released. The Purchasers shall have no obligation to protect, secure, perfect or insure any Lien at any time held by them as security for the Obligations or for the guarantee contained in this Section 2 or any property subject thereto.

(e)           Guarantee Absolute and Unconditional . Each Guarantor waives any and all notice of the creation, renewal, extension or accrual of any of the Obligations and notice of or proof of reliance by the Purchasers upon the guarantee contained in this Section 2 or acceptance of the guarantee contained in this Section 2; the Obligations, and any of them, shall conclusively be deemed to have been created, contracted or incurred, or renewed, extended, amended or waived, in reliance upon the guarantee contained in this Section 2; and all dealings between the Company and any of the Guarantors, on the one hand, and the Purchasers, on the other hand, likewise shall be conclusively presumed to have been had or consummated in reliance upon the guarantee contained in this Section 2. Each Guarantor waives to the extent permitted by law diligence,
presentment, protest, demand for payment and notice of default or nonpayment to or upon the Company or any of the Guarantors with respect to the Obligations. Each Guarantor understands and agrees that the guarantee contained in this Section 2 shall be construed as a continuing, absolute and unconditional guarantee of payment and performance without regard to (a) the validity or enforceability of the Purchase Agreement or any other Transaction Document, any of the Obligations or any other collateral security therefor or guarantee or right of offset with respect thereto at any time or from time to time held by the Purchasers,

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(b) any defense, set-off or counterclaim (other than a defense of payment or performance or fraud  or misconduct by Purchasers) which may at any time be available to or be asserted by the Company or any other Person against the Purchasers, or (c) any other circumstance whatsoever (with or without notice to or knowledge of the Company or such Guarantor) which constitutes, or might be construed to constitute, an equitable or legal discharge of the Company for the Obligations, or of such Guarantor under the guarantee contained in this Section 2, in bankruptcy or in any other instance. When making any demand hereunder or otherwise pursuing its rights and remedies hereunder against any Guarantor, the Purchasers may, but shall be under no obligation to, make a similar demand on or otherwise pursue such rights and remedies as they may have against the Company, any other Guarantor or any other Person or against any collateral security or guarantee for the Obligations or any right of offset with respect thereto, and any failure by the Purchasers to make any such demand, to pursue such other rights or remedies or to collect any payment