We examined clinical features in 877 in- and outpatients affected by depression who were enrolled in psychopharmacological trials, subdivided according to Hollingshead's method into five social classes. The results showed that social class correlated significantly with the subtypes of mood disorders, with bipolar disorder being more frequent amongst the upper than the lower social classes. Furthermore, as already reported in other countries, social class appeared to influence the psychopathological pattern of depressive symptoms: somatization and anxiety were more frequent amongst the lower social classes, while psychic and cognitive symptoms were more common amongst the upper classes.