Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands	6 Months Ended			128 Months Ended
	Jun. 30, 2011		Jun. 30, 2010	Jun. 30, 2011
Cash flows from operating activities:
Net loss	$ (17,421)		$ (26,305)	$ (328,614)
Adjustments to reconcile net loss attributable to Alexza common stockholders to net cash provided by (used in) operating activities:
Share-based compensation	823		3,286	22,682
Extinguishment of officer note receivable				2,300
Change in fair value of contingent liability	300		1,171	3,445
Issuance of common stock for intellectual property				92
Charge for acquired in-process research and development				3,916
Amortization of assembled workforce				222
Amortization of debt discount and deferred interest	247		8	937
Amortization of premium (discount) on available-for-sale securities	142		27	(279)
Depreciation and amortization	2,247		2,311	28,413
Write-off of other asset				2,800
(Gain)/loss on disposal of property and equipment			(5)	205
Changes in operating assets and liabilities:
Other receivables			1,406
Prepaid expenses and other current assets	244		68	(715)
Other assets	(140)		1,031	(2,836)
Accounts payable	(482)		174	2,170
Accrued clinical and other accrued liabilities	(185)		(53)	(511)
Deferred revenues	(555)		40,000	3,776
Other liabilities	(1,158)		22	16,841
Net cash provided by (used in) operating activities	(15,938)		23,141	(245,156)
Cash flows from investing activities:
Purchases of available-for-sale securities	(22,794)		(29,958)	(424,400)
Maturities of available-for-sale securities	27,659		8,961	401,911
Purchases of available-for-sale securities held by Symphony Allegro, Inc.				(49,975)
Maturities of available-for-sale securities held by Symphony Allegro, Inc.				45,093
(Increase)/decrease in restricted cash				(400)
Purchases of property and equipment	(242)		(6,824)	(50,766)
Proceeds from disposal of property and equipment				57
Cash paid for merger				(250)
Net cash provided by (used in) investing activities	4,623		(27,821)	(78,730)
Cash flows from financing activities:
Proceeds from issuance of common stock, common stock warrants and exercise of stock options and stock purchase rights, net of offering costs	16,145		563	178,352
Repurchases of common stock				(8)
Proceeds from issuance of convertible preferred stock				104,681
Proceeds from repayment of stockholder note receivable				29
Proceeds from purchase of noncontrolling interest in Symphony Allegro, Inc				4,882
Proceeds from purchase of noncontrolling interest by preferred shareholders in Symphony Allegro, Inc, net of fees				47,171
Payments of contingent payments to Symphony Allegro Holdings, LLC.			(7,500)	(7,500)
Proceeds from financing obligations			14,806	33,738
Payments of financing obligations	(2,629)		(2,417)	(21,587)
Net cash provided by financing activities	13,516		5,452	339,758
Net increase (decrease) in cash and cash equivalents	2,201		772	15,872
Cash and cash equivalents at beginning of period	13,671	[1]	13,450
Cash and cash equivalents at end of period	$ 15,872		$ 14,222	$ 15,872

[1] The condensed consolidated balance sheet at December 31, 2010 has been derived from audited consolidated financial statements at that date.