Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended			141 Months Ended
	Sep. 30, 2012		Sep. 30, 2011	Sep. 30, 2012
Cash flows from operating activities:
Net loss	$ (17,705)		$ (30,838)	$ (369,429)
Adjustments to reconcile net loss attributable to Alexza common stockholders to net cash provided by (used in) operating activities:
Share-based compensation	2,476		1,494	26,741
Change in fair value of contingent liability	(1,000)		3,300	6,145
Extinguishment of officer note receivable				2,300
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	350		353	1,642
Amortization of premium (discount) on available-for-sale securities	1		180	(216)
Write off of other asset				2,800
Depreciation and amortization	3,467		3,371	34,065
Gain on disposal of property and equipment	(409)			(204)
Changes in operating assets and liabilities:
Other receivables	10,000
Prepaid expenses and other current assets	(117)		79	(760)
Other assets			(133)	(2,843)
Accounts payable	(1,771)		345	1,703
Accrued clinical and other accrued liabilities	(688)		828	(1,512)
Deferred revenues	(1,890)		(1,814)	8,744
Other liabilities	(3,700)		(1,746)	11,964
Net cash provided used in operating activities	(10,986)		(24,581)	(274,630)
Cash flows from investing activities:
Purchases of available-for-sale securities			(26,456)	(430,071)
Maturities of available-for-sale securities	2,000		36,237	430,288
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 noncurrent restricted cash	200			(200)
Purchases of property and equipment	(214)		(409)	(51,234)
Proceeds from disposal of property and equipment	425			482
Cash paid for merger				(250)
Net cash used in operating activities	2,411		9,372	(55,867)
Cash flows from financing activities:
Proceeds from issuance of common stock and warrants and exercise of stock options and stock purchase rights	35,177		16,144	213,529
Repurchase 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.	(5,000)			(12,500)
Change in current restricted cash	(6,469)			(6,469)
Proceeds from financing obligations, net of issuance costs				33,738
Payments of financing obligations	(4,520)		(4,103)	(29,041)
Net cash provided by (used in) financing activities	19,188		12,041	356,012
Net increase (decrease) in cash and cash equivalents	10,613		(3,168)	25,515
Cash and cash equivalents at beginning of period	14,902	[1]	13,671
Cash and cash equivalents at end of period	$ 25,515		$ 10,503	$ 25,515

[1] The condensed consolidated balance sheet at December 31, 2011 has been derived from audited consolidated financial statements at that date.