Review of 60 consecutive records of patients who died before the age of 53 years in a state mental hospital revealed that 27 of those patients (45%) had a schizophrenic disorder. Of those 27 patients, five (18.5%) died of the complications of self-induced water intoxication and schizophrenic disorders (SIWIS). Clinical, laboratory, and autopsy features of those five SIWIS patients and of an additional five SIWIS cases obtained from the literature include psychosis, polydipsia, polyuria, severe hyposthenuria (specific gravity 1.003 or less), hyponatremia, seizures, coma, and cerebral and visceral edema. SIWIS characteristically develops during Arieti's third or "preterminal" stage (5 to 15 years after onset of psychosis) of schizophrenic disorders and it must be included in the differential diagnosis of unexplained death among psychiatric patients. As there are no pathognomonic SIWIS tissue changes, the pathologist must carefully integrate clinical, laboratory, and autopsy findings to arrive at the proper diagnosis. When premortem findings of polydipsia and hyponatremia are not available, evidence of antecedent severe hyposthenuria and postmortem vitreous humor hyponatremia of less than 120 mEq/1 are strongly supportive of the diagnosis of death due to SIWIS.