This paper presents the prevalence rates of schizophrenia and major affective disorders by age and race among a random sample of male jail detainees. Subjects were administered the National Institute of Mental Health Diagnostic Interview Schedule (NIMH-DIS). The jail prevalence rates were then compared with general population data from the five-city Epidemiologic Catchment Area program using difference of proportion tests and loglinear analysis. After controlling for demographic differences between the jail and five-city samples, the jail prevalence rates were still two to three times higher than those in the general population. These findings suggest several public policy modifications concerning the psychiatric management of our burgeoning jail population.