Alexza Pharmaceuticals (ALXA) 10-K 2006 FY Annual report

Exhibit 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the incorporation by reference in the Registration Statement on Form S-8 (No. 333-132593) pertaining to the 2005 Equity Incentive Plan, the 2005 Non-Employee Directors’ Stock Option Plan and the 2005 Employee Stock Purchase Plan of Alexza Pharmaceuticals, Inc. of our report dated March 27, 2007 with respect to the consolidated financial statements of Alexza Pharmaceuticals, Inc. included in this Annual Report (Form 10-K) for the year ended December 31, 2006.

/s/ Ernst & Young LLP

Palo Alto, California
March 27, 2007