The rationale and design of a large, multicentre, prospective follow-up study on the outcome of severe mental disorders is presented. The study is currently under way in Italy, where psychiatric care has been uniquely characterised since 1978 by the statutory prohibition of admitting patients to psychiatric hospitals. The main purpose of the study is to describe the 5-year outcome of patients with a diagnosis of schizophrenia, paranoid disorder, affective psychosis, reactive psychosis or personality disorder with respect to five areas (clinical condition, personal autonomy, work, and family and social relationships); a secondary objective is to describe the heterogeneity of practices and resources of psychiatric services. The study is being carried out by 76 outpatient psychiatric services throughout the country, covering approximately one-tenth of the Italian population.