Background: While several articles on MD-PhD trainees in the basic sciences have been published in the past several years, very little research exists on physician-investigators in the social sciences and humanities. However, the numbers of MD-PhDs training in these fields and the number of programs offering training in these fields are increasing, particularly within the US. In addition, accountability for the public funding for MD-PhD programs requires knowledge about this growing population of trainees and their career trajectories. The aim of this paper is to describe the first cohorts of MD-PhDs in the social sciences and humanities, to characterize their training and career paths, and to better understand their experiences of training and subsequent research and practice. Methods: This paper utilizes a multi-pronged recruitment method and novel survey instrument to examine an understudied population of MD-PhD trainees in the social sciences and humanities, many of whom completed both degrees without formal programmatic support. The survey instrument was designed to collect demographic, training and career trajectory data, as well as experiences of and perspectives on training and career. It describes their routes to professional development, characterizes obstacles to and predictors of success, and explores career trends. Results: The average length of time to complete both degrees was 9 years. The vast majority (90%) completed a clinical residency, almost all (98%) were engaged in research, the vast majority (88%) were employed in academic institutions, and several others (9%) held leadership positions in national and international health organizations. Very few (4%) went into private practice. The survey responses supply recommendations for supporting current trainees as well as areas for future research. Conclusions: In general, MD-PhDs in the social sciences and humanities have careers that fit the goals of agencies providing public funding for training physician-investigators: they are involved in mutually-informative medical research, clinical practice, and teaching -working to improve our responses to the social, cultural, and political determinants of health and health care. These findings provide strong evidence for continued and improved funding and programmatic support for MD-PhD trainees in the social sciences and humanities.