Basis of Presentation

6 Months Ended

Jun. 30, 2011

Basis of Presentation and Revenue from Collaboration Agreement [Abstract]

Basis of Presentation

Note 1. Basis of Presentation

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. The condensed consolidated balance sheet at December 31, 2010 has been derived from the audited financial statements at that date, but does not include all of the information and footnotes required by GAAP for complete financial statements. This Form 10-Q should be read in conjunction with the Consolidated Financial Statements and accompanying Notes contained in the Onyx Pharmaceuticals, Inc. (the “Company” or “Onyx”) Annual Report on Form 10-K for the year ended December 31, 2010.

Significant Accounting Policies

As of June 30, 2011, there have been no material changes to the Company’s significant accounting policies, compared to the significant accounting policies described in the Company’s Annual Report on Form 10-K for the year ended December 31, 2010.

Use of Estimates and Assumptions

The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Thus, actual results could differ from those estimates. In the opinion of management, all adjustments consisting of normal recurring accruals considered necessary for a fair presentation have been included. Operating results for the three and six months ended June 30, 2011 are not necessarily indicative of the results that may be expected for the year ending December 31, 2011 or for any other future operating periods.

Principles of Consolidation

The unaudited Condensed Consolidated Financial Statements include the accounts of the Company and its wholly owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation.

Segment Reporting

The Company operates in one segment — the discovery and development of novel cancer therapies.

Recent Accounting Pronouncements

In June 2011, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) ASU No. 2011-05, “Presentation of Comprehensive Income” which was issued to enhance comparability between entities that report under U.S. GAAP and IFRS, and to provide a more consistent method of presenting non-owner transactions that affect an entity’s equity. ASU 2011-05 eliminates the option to report other comprehensive income and its components in the statement of changes in stockholders’ equity and requires an entity to present the total of comprehensive income, the components of net income and the components of other comprehensive income either in a single continuous statement or in two separate but consecutive statements. This pronouncement is effective for fiscal years, and interim periods within those years, beginning after December 15, 2011. Early adoption of the new guidance is permitted and full retrospective application is required. The Company does not expect that the adoption of this accounting standard update will have any material impact on its results of operations or financial position.

In May 2011, the FASB issued ASU No. 2011-04, “Amendments to Achieve Common Fair Value Measurement and Disclosure Requirements in U.S. GAAP and International Financial Reporting Standards (“IFRS”).” This pronouncement was issued to provide a consistent definition of fair value and ensure that the fair value measurement and disclosure requirements are similar between U.S. GAAP and IFRS. ASU 2011-04 changes certain fair value measurement principles and enhances the disclosure requirements particularly for Level 3 fair value measurements. This pronouncement is effective for reporting periods beginning on or after December 15, 2011, with early adoption prohibited. The new guidance will require prospective application. The Company is currently evaluating the impact, if any, that the adoption of this pronouncement may have on its results of operations or financial position.