Although clinical investigators are regarded as an endangered species, no systematic investigation of the factors that influence doctor participation in clinical research has previously been performed. The objective of this study was to evaluate the influences of selected aspects of medical education, specialty selection and practice type upon current involvement in clinical research. Data were obtained by a mail survey of 428 graduates from the 1985-95 classes of the Penn State College of Medicine. Among the 34% (n = 145) of doctors who were currently participating in clinical research, there was a higher rate of participation among those in medical and surgical specialties versus those in primary care or hospital-based specialties. Of those participating in clinical research, 46% (n = 65) had sought external funds for their research, and 82% (n = 51) of that group had been awarded funds. Those who had been awarded funds as the percentage of their time involved in clinical research increased were more likely to report that research carried out in medical school had positively influenced their current involvement in clinical research (P = 0.004). The gender distribution among both this latter funded group and the larger group of 145 who were participating in clinical research was 72% men and 28% women, whereas the gender distribution among all respondents was 60% men and 40% women. The 283 individuals who were not participating in clinical research cited financial, family, career plan and practice philosophy as reasons for not doing so. The authors conclude that participation in medical research as a medical student may be under-recognised as a determinant of future involvement in clinical research and that the gender disparity of young doctors entering clinical research must be addressed.