Dr. Francis Collins, NIH Director, convened and charged the Physician-Scientist Workforce Working Group (PSW-WG) with analyzing the current composition and size of the physician-scientist biomedical workforce and making recommendations for actions that NIH should take to help sustain and strengthen a robust and diverse PSW. The need for the PSW-WG emerged from the recommendations of the Biomedical Research Workforce Working Group for strengthening the biomedical workforce. Its June 2012 report concluded that the training and career paths of physician-scientists were different than that of the non-clinician PhD workforce and that further study of this important segment of the workforce was needed.Warning bells about the health of the physician-science workforce were sounded as early as 1979 when future NIH Director James Wyngaarden observed that the physician-scientist with a medical degree was becoming "an endangered species." He had observed that MD applicants for NIH project grants represented a progressively smaller fraction of all applicants than previously, while the corresponding fraction of PhD applicants had increased dramatically. In 1996, NIH established a committee headed by David G. Nathan to make recommendations about the perceived shortfall of clinician scientists. The Nathan Committee recommended creating new career development grants for patient-oriented research and loan repayment programs to help young physician-scientists pursue research careers despite an increasing load of educational debt.In spring 2013, the PSW-WG met and established subcommittees to discuss issues confronting the physician-scientist workforce. To inform its deliberations, the PSW-WG directed quantitative analyses of NIH IMPACII and other relevant databases to answer key questions, and considered the findings from qualitative research based on focus groups and interviews with students, research deans, and early career investigators.The PSW-WG defined physician-scientists as scientists with professional degrees who have training in clinical care and who are engaged in independent biomedical research. The PSW thus includes individuals with an MD, DO, DDS/DMD, DVM/VMD, or nurses with research doctoral degrees who devote the majority of their time to biomedical research. The PSW-WG recognizes that the primary goal of professional clinical education is the training of a skilled clinical workforce in the respective areas of practice, and that the portion of such professionals devoted to research will be small. However, findings which lead to advances in practice are driven largely by the work of investigators with a variety of degrees, of whom those with clinical training contribute essential knowledge and skills.