This paper reviews the literature on the relationship of social class status to the incidence and prevalence of mental disorder. For purposes of this review, social class is divided into three categories: the ‘affluent’, ‘working class’ and ‘poor’. Mental disorders referred to are: schizophrenia, manic-depressive psychosis, psychoneurosis, diseases of the senium, personality disorders and the combined category ‘mentally ill’. The general conclusion is drawn that the rate of existing mental disorder among the poor is substantially higher than among the affluent or working-class groups. This notwithstanding, low social-class status is held to be unrelated to the incidence of functional psychosis (i.e., schizophrenia and manic-depres