All schizophrenic patients admitted consecutively either to the Psychiatric Hospital of the University of Munich (group 1, N = 183) or the Mental State Hospital Haar/Munich (group 2, N = 447) between 1.8.1989 and 1.2.1990 were examined to assess prevalence estimates for substance abuse in schizophrenic inpatients. Psychiatric diagnosis were made according to ICD-9 criteria. Psychopathology and psychosocial variables were documented by means of the AMDP-protocol on admission and discharge. The diagnostic procedure included a detailed semi-structured interview concerning the individual alcohol and drug history and sociodemographic data, the Munich Alcoholism Screening Test (MALT), a physical examination and the screening of various laboratory parameters such as GGT and MCV, among others. The results show that substance abuse is a very common problem in schizophrenics. Lifetime prevalence rates for substance abuse were estimated at 21.8% in group 1 and 42.9% in group 2, 3-month prevalence rates for substance abuse were estimated at 21.3% resp. 29.0%. Alcohol abuse was by far the most common type of abuse with prevalence estimates being 17.4% resp. 34.6%. Prevalence rates for substance abuse were much higher in the more "chronic"sample of the Mental State Hospital and in male patients. With respect to schizophrenic subtype few differences could be demonstrated with drug dependence being more common in patients with paranoid schizophrenia. The MALT proved to be a valuable screening instrument for alcohol abuse in schizophrenics with both a high specificity and sensitivity. "Dual diagnosis" schizophrenics had a significantly higher rate of suicide attempts and were less likely to be married. Possible clinical implications of these findings are discussed.