Prescribing patterns of antidepressant drugs were studied, over a period of 30 months, in a random sample of 8743 residents of the area of Rome, Italy. Data from the regional outpatient drug monitoring system were used. The proportion of subjects receiving, during the study period, at least one prescription of antidepressant drugs, was 5.4%; the female-to-male ratio was 2.1. Consumption prevalence increased with age. The single most prescribed drug was fluoxetine followed by amitriptyline and ademetionine. For a surprisingly high proportion of subjects, the observed length of treatment was shorter than expected on the basis of current knowledge in clinical pharmacology. Inappropriate diagnostic and therapeutic procedures are likely explanations.