Causes of death were studied in a cohort of 200 schizophrenic, 100 manic, and 225 depressive patients who were followed in a historical prospective study. These patients were admitted between 1934 and 1944 and were studied 30 to 40 years later. Five cause of death categories were considered in this analysis: (1) unnatural deaths, (2) neoplasms, (3) diseases of the circulatory system, (4) infective and parasitic diseases, and (5) other causes. For each cause of death, the expected number of deaths was calculated from vital statistics for the State of Iowa for the time period of follow-up. Observed numbers of deaths were contrasted with expected numbers of deaths to assess statistical significance for each diagnostic group. There was a significant excess of unnatural deaths in all diagnostic groups in both sexes, with the exception of female manics. This group, however, did show a significant excess of circulatory system deaths. Both male and female schizophrenics showed a substantial excess of infective disorder deaths.