Health policy makers, legislators, providers, payers, and a broad range of other players in the health care market routinely seek information on hospital financial performance. Yet the data at their disposal are limited, especially since hospitals' audited financial statements—the “gold standard” in hospital financial reporting —are not publicly available in many states. As a result, the Medicare Cost Report (MCR), filed annually by most U.S. hospitals in order to receive payment for treating Medicare patients, has become the primary public source of hospital financial information. However, financial accounting elements in the MCR are unreliable,poorly defined, and lacking in critical detail. Comparative analyses of MCRs and matched, audited financial statements reveal long-standing problems with the MCR's data, including major differences in reported profits; variations in the reporting of both revenues and expenses; an absence of relevant details,such as charity care, bad debt, operating versus nonoperating income, and affiliate transactions; an inconsistent classification of changes in net assets; and a failure to provide cash flow statements. Because of these problems, MCR financial data give only a limited and often inaccurate picture of the financial position of hospitals. Audited financial statements provide a more complete perspective, enabling analysts to address important questions left unanswered by the MCR data. Regulatory action is needed to create a national database of financial information based upon audited statements.