Objective - Following the introduction of guidelines of rational drug use, the pharmacoepidemiology of psychotropic drugs was investigated in a sample of long-stay patients living in a Italian psychiatric hospital. Design - Aprospective, longitudinal two-year follow-up study was carried out. Information about sociodemographic and clinical characteristics of the inpatientpopulation, and about medications prescribed, was collected at baseline and after one and two years of follow-up. Setting - Three wards of the psychiatric hospital of Milan. Main outcome measures - Number of patients taking psychotropic drugs, number of patients taking more than one neuroleptic or benzodiazepine, mean neuroleptic dose, psychopatological status according to the Brief Psychiatric Rating Scale (BPRS). Results 70 patients were recruited and followed for two years. At follow-up a reduction in the number of patients taking neuroleptic drugs was recorded, together with a 50% decrease in the number of patients taking more than one neuoleptic. A reduction in the use of depot formulations was in addition shown. Patients taking benzodiazepines decreased of 50%. According to the BPRS, no psychopatological changes were observed during the study. Conclusions - These data suggest that education in psychopharmacology may guide towards a more rational use of drugs; longitudinal clinical audits should be implemented to monitor everyday practice.