With the International Accounting Standards Committee (IASC) reaching the completion of its core standards program, the International Organization of Securities Commissions (IOSCO) is considering its response to the IASC's application for endorsement of International Accounting Standards (IASs). A critical aspect of IOSCO's acceptance of IASs is likely to be the extent to which such standards are compatible with US Generally Accepted Accounting Principles (US GAAP). This issue is explored by an empirical study of US GAAP reconciliations by non-US companies complying with IASC standards. The results indicate that the impact of accounting differences between IASs and US GAAP is narrowing and suggest that the Securities Exchange Commission (SEC) should consider accepting IASC standards without condition. Alternatively, an SEC endorsement could include a short list of IASs where acceptance is subject to additional disclosures.