The Food and Drug Administration (FDA) has issued draft guidelines that would require more rigorous standards for making pharmacoeconomic claims. This paper critiques the guidelines and explores the objectives of market regulation for health-related cost and effectiveness information on pharmaceutical products. It argues that the FDA should proceed with caution and flexibility. In particular, regulations should recognize the potential usefulness of pharmacoeconomic information in helping health care decisionmakers make better-informed choices. They also should acknowledge the enhanced ability of those using the information to evaluate pharmacoeconomic studies and the degree to which the various players in the market can impose their own regulatory discipline.