A mortality study was performed on 1190 patients with schizophrenia discharged from hospitals in Stockholm County during 1971. By means of a linkage between the Stockholm County inpatient register and the national cause-of-death register, all deaths through 1981 were identified. Compared with the general population, the schizophrenics had an approximately twofold increase in overall mortality. The excess mortality was found in all causes of death but was particularly high in "unnatural death". The suicide mortality was approximately ten times higher among male schizophrenics and 18 times higher among female schizophrenics than in the general population. The methodologic problems with register studies are numerous, but the medical information system used in the study is of great value for psychiatric epidemiologic research.