This paper examines conservatism in accounting. Conservatism is defined as the differential verifiability required for recognition of profits versus losses. In its extreme form the definition incorporates the traditional conservatism adage: quot;anticipate no profit, but anticipate all losses.quot; Despite criticism from many quarters, including standard-setters, conservatism appears not only to have survived in accounting for many centuries, but also to have increased in the last 30 years.The paper lays out the various alternative explanations for conservatism: contracting; shareholder litigation; taxation and accounting regulation (e.g., SEC and FASB). It also summarizes the empirical evidence on the existence of conservatism and the extent to which it is consistent with the alternative explanations for conservatism. The evidence is consistent with both the existence of conservatism and its increase in recent years. Contracting and shareholder litigation explanations appear to be important in these results. The evidence on the effect of taxation and regulation is weaker, but is still consistent with those explanations playing a role. Earnings management could also produce some of the evidence on conservatism, but it is unlikely to be the major explanation.The explanations and evidence have important implications for accounting regulators (SEC and FASB). First, the contracting explanation implies that conservatism will exist even in the absence of formal contractual use of financial statements. As long as income and net asset measures have meaning and are used in a way that affects management's welfare, conservatism is likely to be an optimal accounting principle. Absent differential verifiability, financial measures such as income and net assets are likely to be subject to sufficient manipulation to render them meaningless. Second, recent FASB moves to apply rules such as mark-to-market without appropriate concern for verifiability are likely to be disastrous for the FASB and capital markets. Third, attempts to introduce unverifiable estimates of future cash flows into the financial statements are likely to just as disastrous.