A speculative hypothesis is presented which links the late development of modern concepts of schizophrenia with social and familial effects of industrialization. It is suggested that the social and family structures found historically in pre-industrial societies and currently in developing countries exert a comparatively benign effect upon patients with schizophrenia, and that these effects are lost during and after industrialization. Thus the severe and chronic forms of the illness became prominent and therefore recognized in the segregated institutions of Europe in the latter part of the nineteenth century. Possible mechanisms are examined by which industrialization could influence the structure of communities and families and the development of individuals to produce the postulated changes in the individual's response to the schizophrenic illness. It is suggested that three major areas of interest for the identification of these mechanisms are (i) the rapid increase in size of towns and communities, (ii) changes in perinatal and infant mortality and morbidity, and (iii) changes in family structure. Some ways of testing the hypothesis and its implications are outlined.