The purpose of the study was to examine first-admitted patients with delusional psychosis meaning functional psychosis with paranoid symptoms with respect to clinical course and outcome. The index population comprised 88 patients. At discharge from first admission the patients were classified according to ICD-8 and DSM-III. According to both diagnostic classifications the majority of the patients did not belong to either of the two major psychotic groups, schizophrenia or affective psychosis. During the 2-year observation period half of the patients took psychotropic drugs continuously, and almost half of the patients experienced one or more relapses. One third of the patients were readmitted, and in average the patients stayed in the hospital for 4 months during the observation period including the time of index admission. At follow-up half of the patients revealed positive psychotic symptoms, while two thirds were moderately or severely impaired because of psychotic illness or personality dysfunction. It is concluded that the present aftercare treatment is insufficient to prevent relapse and psychotic symptoms. In consequence of this the existence of delusions at first admission to hospital because of functional psychosis seems for many to predict an unfavourable course and outcome. Further study will search for clinical and social predictors of course and outcome in patients with delusional psychosis.