From 1962 to 1991, 150 students earned both the M.D. and the Ph.D. degrees in a combined program of study at The Johns Hopkins University School of Medicine (JHUSM). Seventy-five of these individuals were supported by the Medical Scientist Training Program (MSTP) of the National Institutes of Health. The authors analyzed the professional development of these dual-degree recipients, focusing particularly on the 109 M.D.-Ph.D.s who graduated since 1980, when the first MSTP-supported student received both degrees. Of the 109 graduates since 1980, 42 are now in career positions. Thirty-four of the 42 graduates (81%) obtained clinical housestaff training, and 21 of the 34 also had postdoctoral science training. Nearly all of the 42 M.D.-Ph.D.s are in full-time academic posts (81%) or positions in research institutes (14%); the remaining 5% hold research positions in biotechnology firms. All 42 graduates are actively involved in research, and 67% have regular and well-defined clinical responsibilities. Analysis of the representation of M.D.-Ph.D.s on the JHUSM faculty from 1962 to 1991 shows a striking increase with time in the percentage of M.D.-Ph.D.s among the full-time faculty, particularly at the level of assistant professor. These findings suggest that M.D.-Ph.D. graduates nationwide are being recruited in increasing numbers to medical school faculties and are pursuing medical careers encompassing both research and clinical practice.