1.	You indicate that $24 million of the accounts receivables affected by the credit and economic conditions in Europe have been outstanding for greater than a year for which you have recorded an allowance of $3.5 million. Please tell us why you believe the remaining amount is still collectible.

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2.

You have $540.9 million in cash and cash equivalents at December 31, 2011 and foreign operations are becoming increasingly significant to your business. Please provide proposed revised disclosure to be included in future periodic reports of the amount of cash and investments that are currently held by your foreign subsidiaries that are considered reinvested indefinitely and its expected effect on your liquidity and capital resources. Refer to Item 303(a)(1) of Regulation S-K and Section IV of SEC Release 33-8350.

3.	The Healthcare Reform Act requires many changes for the pharmaceutical industry, including an annual fee to be assessed on pharmaceutical manufacturers, changes in Medicaid

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•	The Act mandated an annual fee payable by branded prescription drug manufacturers and importers on branded prescription drugs. Due to the orphan drug status of our only marketed product, Soliris, we are currently exempt from paying this annual fee.

•	Manufacturers of pharmaceutical products are required to be responsible for 50% of a patient's cost of branded prescription drugs related to the Medicare Part D Coverage Gap (the “Coverage Gap”). Medicare patients typically receive Soliris therapy under Medicare Part B rather than Part D, and therefore, the financial exposure for the Coverage Gap is not material to our results.

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Manufacturers are also subject to an increase in rebates associated with Medicaid recipients and an expansion of the rebate to managed Medicaid organizations, and we have appropriately adjusted our accruals for governmental rebates, the results of which, in total, also were not material to our results. Furthermore, Soliris is exempt from the expansion of 340(B) eligible entities under the Act, due to its orphan drug status.

4.

You state that "For products with an approved indication, raw materials and purchased drug product associated with clinical development programs are included in inventory and charged to research and development expense when consumed. For products without an approved indication, purchased drug product is charged to research and development expense upon final quality release. We also capitalize the cost of inventory manufactured at our manufacturing

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•	Clarify what you mean by "for products with an approved indication" and "for products without an approved indication". Clarify if these costs relate to inventory capitalized prior to regulatory approval or if the costs relate to products that are purchased to be used in research and development activities.

•	Clarify what you mean by "final quality release" and why you believe that is the point in time in which research and development expense should be recorded.

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Clarify how the costs that you capitalize at your manufacturing plant are accounted for after the manufacturing facility is approved and how the costs are expensed in the financial statements. State if the inventory produced can be sold after approval. Clarify if the costs are recorded as cost of goods sold if the product is sold or expensed as depreciation expense once the manufacturing plant is approved.

•	Clarify how you account for the costs of inventory relating to getting manufacturing plant approval in which the validation batches are not successful.

•	Tell us the accounting literature you used to support your accounting treatment for the capitalization of inventory.

•	If material, separately disclose the inventory capitalized relating to inventory available for sale, inventory produced prior to regulatory approval, and inventory to be used in research and development activities separately by each category of raw materials, work in-process, and finished goods.

•	Clarify what you mean by "for products with an approved indication" and "for products without an approved indication". Clarify if these costs relate to inventory capitalized prior to regulatory approval or if the costs relate to products that are purchased to be used in research and development activities.

•	Clarify what you mean by "final quality release" and why you believe that is the point in time in which research and development expense should be recorded.

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Clarify how the costs that you capitalize at your manufacturing plant are accounted for after the manufacturing facility is approved and how the costs are expensed in the financial statements. State if the inventory produced can be sold after approval. Clarify if the costs are recorded as cost of goods sold if the product is sold or expensed as depreciation expense once the manufacturing plant is approved.

•	Clarify how you account for the costs of inventory relating to getting manufacturing plant approval in which the validation batches are not successful.

•	Tell us the accounting literature you used to support your accounting treatment for the capitalization of inventory.

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•	If material, separately disclose the inventory capitalized relating to inventory available for sale, inventory produced prior to regulatory approval, and inventory to be used in research and development activities separately by each category of raw materials, work in-process, and finished goods.

5.	You state "it is not practical to estimate the amount of additional taxes which might be payable on our undistributed earnings". Please provide proposed revised disclosure to be included in future periodic reports to indicate whether such estimate is practicable. Refer to ASC 740-30-50-2c.

•	Alexion is responsible for the adequacy and accuracy of the disclosure in the filing;

•	Staff comments or changes to disclosure in response to Staff comments do not foreclose the Commission from taking any action with respect to the filing; and

•	Alexion may not assert Staff comments as a defense in any proceeding initiated by the Commission or any person under the federal securities laws of the United States.

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