To determine the number, personal and professional characteristics, and attitudes of part-time medicine faculty. Part-time faculty in departments of medicine were identified by the chairs of medicine and faculty roster representatives of the Association of American Medical Colleges for each U.S. medical school and by a survey of faculty. A 79-item questionnaire including questions about working conditions, attitudes toward professional and personal issues, and institutional policies. A total of 245 eligible questionnaires were returned (69% of the estimated number of eligible part-time faculty). Sixty-three percent were men and 27% were women. Women faculty worked an average of 35 h/wk, combining their careers with childbearing, whereas men worked 51 h/wk, divided between their faculty position and private practice. Respondents' work time was devoted to teaching and patient care, with no time dedicated for research. Most faculty (86%) were in nontenured track positions; approximately one half (47%) developed the position themselves. Only 8% reported that existing institutional policies allowed part-time faculty more time to reach promotion and tenure standards. A high degree of career satisfaction existed (mean score, 8.6 on a 10-point scale) even though faculty believe that part-time status makes promotion more difficult and negatively influences colleagues' perceptions of them. We estimate that more than 400 faculty work part time in departments of medicine in U.S. medical schools. The majority are men who combine academic careers with private practice. Most part-time faculty work as clinician/teachers in nontenure track positions and are satisfied with their careers.