A review of studies of the prevalence of substance abuse among schizophrenics suggest that both demographic and environmental factors are strong determinants of the extent of substance abuse in this population as well as the type of substances used. In a mid-sized Canadian city, a sample of schizophrenic patients referred to a dual diagnoses clinic were administered the Addiction Severity Index. With age and gender included as a factor, no significant differences were found in the choice or length of use of most drugs between diagnostic groups, contrary to some other reports from large urban centres. Compared with a population of a similar age, there were fewer regular and more former drinkers among the schizophrenic patients. The choice of other substances by the sample reflected the pattern of use in the population at large. This approach to prevalence provides a more balanced perspective of the substance abuse by schizophrenics. The major targets for prevention remain the alcohol, caffeine and tobacco consumption.