We studied the diagnostic stability and the factors associated with it in 1,443 psychiatric patients with multiple admissions for a period of 45 months. We successively considered the whole population, the psychotic and then the schizophrenic patients. Demographic and DSM-III-R diagnostic information was collected on a computerized database. During the observation period, 1,443 patients were hospitalized twice or more. Diagnostic stability ranged from 34 to 86%. Psychotic disorder was the most stable, whereas adjustment and anxiety disorders were the least stable. Among schizophrenic patients, higher stability appeared for residual and disorganized types (83 and 71%, respectively). Statistical analysis did not show any variable associated with change, apart from the diagnoses themselves. The reasons that could explain changes are discussed, as well as the clinical consequences of these shifts.