With recent epidemics of sexually transmitted diseases, it is increasingly important for medical students to be well prepared to take sexual histories. The authors studied this issue through a self-administered questionnaire completed by first-year medical students at two western U.S. medical schools (response rate 87%). Students who were better prepared (i.e., more knowledgeable, more comfortable, more appropriate attitudes) had more personal sexual experience and were more likely to have spoken with either a physician or a patient about a personal sexual concern. Different student characteristics were associated with different domains of preparation for taking a sexual history (e.g., knowledge v.s. attitudes). The educational implications of these findings are discussed.