In a three-year prospective study of service-based incidence of functional psychoses in Africa, 94 cases of brief reactive psychosis were compared with 56 cases of schizophreniform syndromes, 29 cases of DSM-III schizophrenia and 14 of manic-depressive psychosis. This was supplemented by retrospective study of the same syndromes not in their first episode. Brief reactive psychosis was found to be a composite syndrome. The 50% with preceding depression were a distinct group, in terms of course and demographic features. Of those with intense prodromal anxiety, most were a single episode precipitated by a major life event, a few showed a recurrent long-term pattern. Schizophrenia was heralded, or presented unequivocally months or years later, in 10-20%. The schizophreniform group comprised a range of atypical psychoses intermediate between the transient and major psychoses. The pattern of precipitants and the over-representation of education and paid employment in the acute syndromes, compared with the major psychoses, in a society which was largely first-generation educated, suggested a link with rapid social change.