The aim of this study was to examine the hypothesis that differences in outcome among affective and non-affective psychoses are associated with differences in the degree of developmental deviance. We conducted a retrospective survey of first contact cases treated over a 20-year period in a psychiatric hospital serving a catchment area in South London. All patients with non-depressive functional psychosis residing in the catchment area who received their first psychiatric treatment between 1965 and 1984 were included in the study. Cases were classified according to the relative chronicity of their illness into four non-overlapping groups: mania, schizomania, acute schizophrenia and chronic schizophrenia. There was a linear trend in the association between illness chronicity and proxy measures of development deviance, such as premorbid unemployment, single status and poor academic achievement. Compared to individuals with mania, schizophrenic patients had a 3-6 times increased risk of premorbid abnormality. For patients with schizomania and acute schizophrenia, the risk was 1.5-3 times greater than for manic subjects. We conclude that the prevalence of premorbid abnormalities is highest among chronic schizophrenia, but similar disturbances also occur, to a lesser degree, in less disabling affective and non-affective psychotic disorders.