Background: Sexual history and HIV counseling (SHHIVC) are essential clinical skills. Our project's purpose was to evaluate a standardized patient educational intervention teaching third-year medical students SHHIVC. Methods: A four-hour standardized patient workshop was delivered to one-half of the class each of three consecutive years at one medical school. Approximately 3.5 weeks later, all students engaged in a standardized patient examination including one station assessing SHHIVC, answered an open-ended written exercise following the standardized patient encounter, and completed a written examination including sexual history and HIV-related questions. Results: Workshop participants scored higher than non-participants on SHHIVC items on the standardized patient station (P less than 0.0001), written exam (P less than 0.0001), and open-ended written exercise after the standardized patient encounter (P = 0.024). Conclusions: Our SHHIVC curriculum was associated with students demonstrating better clinical skills on a SHHIVC standardized patient examination station and more SHHIVC knowledge on two measures of medical knowledge than students not participating in the SHHIVC educational intervention.