Relatively little is known regarding factors associated with the choice of a research career among practicing physicians, and most investigations of this issue have been conducted in the absence of a theoretical/conceptual model. Therefore we designed a survey to identify the determinants of decisions to pursue a biomedical research career based upon the Theory of Planned Behavior and the concept of stereotype threat. From October 2012 through January 2014 electronic surveys were sent to four consecutive Harvard Medical School graduating classes, 1996-1999. Respondents provided demographic information, indicated their current research involvement, and provided retrospective reports of their experiences and attitudes when they were making career choices as they completed medical school. Multivariable ordinal regression was used to identify factors independently associated with current research involvement. Completed questionnaires were received from 358 respondents (response rate 65%). In unadjusted analyses, variables associated with more extensive research involvement included non-minority status, male gender, lower debt at graduation, strong attitudes toward research at time of graduation, and greater social pressures to pursue research (all P < 0.001). These associations remained significant in multivariable regression analysis (all P < 0.01). However, an interaction between sex and prior research publications was also detected, indicating that more extensive research involvement during medical school doubled the likelihood of a research career for women (OR 2.53, 95% CI 1.00-6.40; P = 0.05). Most of the factors predicting research career choice involve factors that are potentially modifiable, suggesting that appropriately designed behavioral interventions may help to expand the size and diversity of the biomedical research community.