Nuclear medicine practice and work force demographics reflect the historically diverse evolution of this specialty. The most pressing problem for nuclear medicine is a projected shortage of fully trained physicians due to practitioner retirement that is unmatched by residency program output. During the past decade the number of 2-year nuclear medicine residency programs (average of 90) and the total number of residents (average of 191 in both years) have remained remarkably stable. In contrast, the number of 1-year nuclear radiology residency programs, available positions, and residents have declined significantly. A similar decline is seen in radiologists obtaining full nuclear medicine training and American Board of Nuclear Medicine (ABNM) board certification. This void has been filled by nonradiologist trainees who only seek certification by ABNM. Perhaps such shifts in resident profile are an early indicator that the United States is evolving toward practice models in which nuclear medicine is provided by fully trained, full-time physicians, similar to the European work force model. The recent Society of Nuclear Medicine survey of 10,446 physicians who practice nuclear medicine shows a current practice pattern in the United States that is distinctly different from that in Europe. The vast majority of those surveyed practice part time. Only 7% of all physicians who practice nuclear medicine do so full time, (ie more than 90% of the time), but they account for as much full-time employee (FTE) work load as 70% of all part-time physicians. Although the number of radiologists entering nuclear medicine is declining, 51% of total FTE work load is still done by radiologists with only American Board of Radiology certification. Physicians certified by ABNM represent 42% of all FTE work load. Cardiologists certified by American Board of Internal Medicine-Cardiovascular Specialization account for approximately 4% of nuclear medicine (15% of total cardiovascular nuclear medicine) FTE work load. Work force shortage of nuclear medicine technologists remains a chronic problem in spite of extensive study: however, recent predictions suggest some improvement in the future. Solutions to work force problems facing nuclear medicine will require ongoing data surveys, aggressive recruitment of trainees, expansion of training positions, and socioeconomic initiatives that promote desirable future practice models.