Mortality data are presented from a four-decade follow-up study of 200 schizophrenic, 100 manic, 225 depressive patients, and 160 surgical controls (80 appendicectomy; 80 herniorrhaphy). Data for this analysis were available on 648 (95 per cent) members of the study population. Using sex-age standardized mortality ratios (SMR), the mortality experience of the study population was compared with that of the state of Iowa, the geographical area served by the admitting medical facility for the study group. Results are presented for a four-decade period beginning 1935-44, and ending 1965-74. All three psychiatric groups had a significant increase in mortality risk. This was most pronounced in the first decade following admission, although schizophrenic patients, especially females, continued to show a significant excess of deaths throughout the entire four decades of the follow-up period. During no decade of the follow-up period did the mortality of the surgical controls differ significantly from that of the Iowa population.