In preparation for shifting of care from psychiatric hospital to the community, the prevalence of substance abuse comorbidity among discharged psychiatric patients was studied. Such patients are not usually treated by substance abuse programs or mental health clinics. Data from the Israeli National Psychiatric Case Registry were analyzed on reported substance abuse among all 53,379 psychiatric discharges during 1989-92. The Registry consists of data that physicians are mandated to report on all patients. The authors found that reported substance abuse comorbidity was 13.2% for males and 3.6% for females. Patients with a diagnosis of personality disorder had the most reported substance abuse. Reported drug abuse for males increased with age until age 45, and alcohol abuse until age 65. Drug and alcohol abuse by females is the highest for the patients under age 24 and declines with an increase in age. The results were almost identical for each of the four years studied. The results suggest that developing special outpatient facilities to serve this group will be impractical because of the small numbers. Ways of serving these patients in existing community mental health centers are discussed.