Summary: This testimony discusses the long-term viability of the Social Security program. Social Security's Trust Funds will not be exhausted until 2038, but the trustees now project that the program's cash demands on the rest of the federal government will begin much sooner. Aiming for sustainable solvency would increase the chance that future policymakers would not have to face these difficult questions on a recurring basis. GAO has developed the following criteria for evaluating Social Security reform proposals: financing sustainable solvency, balancing adequacy and equity, and implementing and administering reforms. These criteria seek to balance financial and economic considerations with benefit adequacy and equity issues and the administrative challenges associated with various proposals. GAO's recent report on Social Security and income adequacy (GAO-02-62) makes three key points. First, no single measure of adequacy provides a complete picture; each measure reflects a different outlook on what adequacy means. Second, given the projected long-term financial shortfall of the program, it is important to compare proposals to both benefits at currently promised levels and benefits funded at current tax levels. Third, various approaches to benefit reductions would have differing effects on adequacy.