Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	6 Months Ended			138 Months Ended
	Jun. 30, 2012		Jun. 30, 2011	Jun. 30, 2012
Cash flows from operating activities:
Net loss	$ (10,784)		$ (17,421)	$ (362,508)
Adjustments to reconcile net loss attributable to Alexza common stockholders to net cash provided by (used in) operating activities:
Share-based compensation	2,016		823	26,281
Change in fair value of contingent liability	(1,200)		300	5,945
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	246		247	1,538
Amortization of premium (discount) on available-for-sale securities	1		142	(216)
Write off of other asset				2,800
Depreciation and amortization	2,569		2,247	33,167
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	127		244	(516)
Other assets			(140)	(2,843)
Accounts payable	(2,219)		(482)	1,255
Accrued clinical and other accrued liabilities	(727)		(185)	(1,551)
Deferred revenues	(1,161)		(555)	9,473
Other liabilities	(3,185)		(1,158)	12,479
Net cash provided by (used in) operating activities	(4,726)		(15,938)	(268,370)
Cash flows from investing activities:
Purchases of available-for-sale securities			(22,794)	(430,071)
Maturities of available-for-sale securities	2,000		27,659	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 restricted cash				(400)
Purchases of property and equipment	(29)		(242)	(51,049)
Proceeds from disposal of property and equipment	419			476
Cash paid for merger				(250)
Net cash provided by (used in) investing activities	2,390		4,623	(55,888)
Cash flows from financing activities:
Proceeds from issuance of common stock and warrants and exercise of stock options and stock purchase rights	21,782		16,145	200,134
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 restricted cash	(7,847)			(7,847)
Proceeds from financing obligations, net of issuance costs				33,738
Payments of financing obligations	(2,975)		(2,629)	(27,496)
Net cash provided by (used in) financing activities	5,960		13,516	342,784
Net increase (decrease) in cash and cash equivalents	3,624		2,201	18,526
Cash and cash equivalents at beginning of period	14,902	[1]	13,671
Cash and cash equivalents at end of period	$ 18,526		$ 15,872	$ 18,526

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