The incidence of clinically manifest cryptococcosis was determined among over one million subscribers to the Kaiser-Permanente Medical Care Program in Northern California during the 10-year period 1971-1980. A total of 10 persons developed the disease, of whom two had no underlying immunosuppressive disease or therapy. The overall incidence was 0.8 per million persons per year; for nonimmunosuppressed individuals the incidence was estimated to be 0.2 per million per year. Incidence increased with age into the seventh decade of life and was greater in men than in women. The overall case fatality rate was 40 per cent. The data are not consistent with the view that cryptococcosis usually occurs in persons without obvious predisposing factors.