This article discusses the history and evolution of the process for generic drug evaluation and approval in the United States, with emphasis on locally acting dermatologic products. The requirements for in vivo bioequivalence (BE) testing and the statistical criteria for BE are discussed, and an example of a topical antifungal dermatologic product is used to demonstrate the BE determination for locally acting drugs. Other factors in the dispensing of prescription medications that are not within the Food and Drug Administration regulatory authority are also mentioned.