Questionnaire II of the National Study of Internal Medicine Manpower was directed to all of the 1502 subspecialty training programs in the United States and Puerto Rico. The overall response rate was 86%. For the years 1972-1973 through 1976-1977 the number of fellows in subspecialty training grew at an average rate of 10.6% per year, or one and one-half times greater than the growth rate of 7.2% in the number of first-year residents in training for the same time period. In 1976-1977 there were 5826 fellows in subspecialty fellowship training, of whom 26% were foreign medical graduates. Stipends for subspecialty fellows in 1976-1977 amounted to $90 million, 40% of which was derived from direct federal funds and 33% from hospital revenues. Most of the subspecialty fellowship programs were in large teaching hospitals, which are closely affiliated with the nation's medical schools. The 1976-1977 professional activities of former subspecialty trainees who had finished their training between 1972 and 1976 were distributed roughly in thirds between research-teaching, teaching-practice, and practice. We discuss public policy implications of the data.