This thesis is concerned with changes over time in the social characteristics of doctors who have entered prepaid group health plans. It focuses on the past social positions which these doctors have occupied and on their status, or rank. The general expectation is that both the rank and positions occupied by doctors prior to entering prepaid group plans have varied as the prestige of these plans has varied. The entrance of physicians into prepaid group health plans was conceptualized as mobility between different contexts of work. Blau’s exchange theory of mobility proved to be the most fruitful source of hypotheses for this study. Blau states that extrinsic rewards are the major incentives for mobility and that intrinsic rewards interact with extrinsic rewards in influencing mobility. From these basic propositions two hypotheses were generated: 1) As the status of prepaid group health plans increases, the status of physicians entering these plans will increase. 2) As the status of prepaid group health plans increases, high status recruits will less frequently come from positions offering intrinsic rewards similar to those found in prepaid group plans. The design of this research was a longitudinal case study. Data were obtained relevant to one prepaid group health plan, the Portland Kaiser Foundation Health Plan. The universe included all physicians who had practiced as full-time, salaried staff in Kaiser at any time since 1945 when Kaiser was first opened to the public. Indicators were obtained from various sources of data. The Kaiser personnel records provided data on physicians’ social characteristics. Data on the status of Kaiser came from an official salary schedule and records of personnel advertisements. Informants were used to rank medical schools and the AMA’s Directory of Approved Internships and Residencies provided a ranking of teaching hospitals. The evidence for the first hypothesis was generally negative. The data indicated that although the status of Kaiser had increased over the years, the status of physicians entering Kaiser had decreased. This conclusion was reached on the basis of findings using prestige of medical school as an indicator for physicians’ achieved status as well as findings using nationality and length of practice as indicators for their ascribed status. Thus, the first hypothesis of this study had to be rejected. The evidence for the second hypothesis was inconclusive: it indicated that as the status of Kaiser increased, the percentage of high status recruits from certain positions with intrinsic rewards similar to Kaiser’s decreased, whereas the percentage from other positions increased. High status physicians have less frequently entered Kaiser a) having held positions emphasizing the scientific aspects of care, b) having memberships in scientific or specialty societies, c) having changed the location of their practice, and d) having changed their specialty. They have more frequently entered Kaiser a) having had postgraduate training b )having had at least five years of training, c) having held jobs in bureaucratic contexts, d) having graduated from medical schools in the North Central and Western states, and e) having engaged in two of more different types of activities. In sum, it was unclear whether the second hypothesis should be accepted or rejected.