The requirement to establish safety of drugs prior to marketing has been in place since 1938 by the US Food, Drug and Cosmetic Act and is by no means a new concept. The efficacy regulations were enacted in 1962 via the Kefauver-Harris Amendment and the drug approval process has evolved thereafter. The assessment of safety and efficacy of drug products is made by pharmaceutical companies during drug development, which then goes through a regulatory review by the US FDA for the determination of market approval or nonapproval. The drug development and regulatory approval processes have endured close ongoing scrutiny by regulatory bodies, the public, US Congress and academic and private organizations and, as a result, have ensured continual refinement. Over the years, evidence has been emerging on varied drug responses in subgroup populations, and the underlying biology associated with age, race and sex as demographic variables have been examined. The resulting growing knowledge of disease burden, treatment response and disparate outcomes has generated opportunities to streamline and improve treatment outcomes in these populations. This article discusses the historical context of women's participation in clinical drug trials submitted to the FDA for regulatory review and approval purposes. The inadvertent consequences of women's exclusion or inadequate representation in past clinical trials and the evidentiary basis for understanding sex differences are also evaluated. Advances in the US regulatory processes to address treatment outcomes that are tied to the topic of this paper, specifically, adverse drug effects in women, are also discussed.