The population of women who sell or exchange sex or intimate sexual services for material goods or services, also called "sex work," often is unrecognized in the typical obstetric and gynecologic practice. The prevalence of this behavior among adult women is difficult to quantify because of its frequent omission from the routine sexual history by women and clinicians. Data on the prevalence of sex work in the United States are largely lacking. The American College of Obstetricians and Gynecologists supports increasing awareness about the health risks, preventive care needs, and limited health care services for female sex workers.