BACKGROUND: Biological sex differences and sociocultural gender norms affect the provision of health care products and services, but there has been little explicit analysis of the impact of sex differences and gender norms on the regulation of pharmaceutical development and marketing. OBJECTIVES: This article provides an overview of the regulation of pharmaceuticals and examines the ways that regulatory agencies account for sex and gender in their review of scientific data and marketing materials. METHODS: The primary focus is on the US context, but information is also included about regulatory models in Europe, Canada, and Japan for comparative purposes. Specific examples show how sex differences and gender norms influence scientific and policy decisions about pharmaceuticals. RESULTS: The United States and Canada were found to be the only countries that have explicit requirements to include women in clinical trials and to perform sex-based subgroup analysis on study results. The potential influence of politics on regulatory decisions may have led to an uneven application of standards, as seen through the examples of mifepristone (for abortion) and sildenafil citrate (for erectile dysfunction). Three detailed case studies illustrate the importance of considering sex and gender in pharmaceutical development and marketing: Phase I clinical trials; human papillomavirus quadrivalent vaccine; and tegaserod, a drug for irritable bowel syndrome. CONCLUSIONS: Sex and gender play important roles in pharmaceutical regulation, from the design of clinical trials and the approval of new drugs to advertising and postmarketing surveillance. However, regulatory agencies pay insufficient attention to both biological sex differences and sociocultural gender norms. This disregard perpetuates inequalities by ignoring drug safety problems that predominate in women and by allowing misleading drug marketing that reinforces gender stereotypes. Recommendations have been made to improve the regulation of pharmaceuticals in regard to sex and gender.