Nationally representative samples of senior physicians, interns and residents, and medical students were interviewed during the spring of 1973. The main focus of the present analysis is senior physicians' responses to national health insurance issues. The level of support among physicians is underestimated by physicians themselves. Despite the fact that 56 per cent of the doctors were in favor of "some form of national health insurance," almost three-fourths of the respondents believed that most doctors they knew personally were opposed. More than four-fifths of the physicians believed that NHI was inevitable, and those who saw NHI as inevitable were more likely to favor it. Doctor's views about NHI were closely related to their general political views. In general, attitudes of AMA members and grass-roots state and local medical society leaders were not greatly divergent. In terms of responses to specific components differentiating NHI alternatives, physicians preferred conservative options on how a program was to be financed and administered as well as whether the development of prepaid groups should be encouraged. Support for the liberal alternative was strongest on the question of peer reviews, with 75 per cet in favor of such reviews under a NHI program. Differentiation in the profession is considerable. Main activity, work setting, specialty, percentage of income in salary, geographical location, and career stage all contribute to differing reactions to NHI among physicians.