This article outlines the history, need, and evolution of gender medicine in emergency care research. Clinical examples are used where sex and gender play a role in diagnosis, management, or prognosis of patients in the emergency department (ED). The ED serves as an ideal setting to advance sex- and gender-specific research as the primary access point for health care for much of the U.S. population, with more than 136 million annual visits. Gender medicine provides the biologic and social framework to provide high-quality, safe, equitable, and cost-effective sex- and gender-specific care in the ED. With a 24-hour hospital presence, and with access to high-acuity patients, emergency physicians are well positioned to lead sex- and gender-specific clinical studies for time-sensitive conditions and also to serve as vital partners in interdisciplinary research projects. The ED also provides the primary access point for less life-threatening conditions such as substance abuse, mental health, and pain management (both acute and chronic). Because one-fifth of the U.S. population is without health insurance, and many more lack a regular provider or rapid access to their providers, the ED is often the only point of contact for advancing gender medicine in this population.