The peripheral-type benzodiazepine receptor (PBR) plays a major role in steroidogenesis. This receptor is sensitive to endocrine changes and stress. Antidepressants have been demonstrated to modulate adrenal and hepatic PBR in rats. To evaluate the relationship between depression and PBR, we measured platelet PBR in untreated depressed patients (n = 14) in comparison to normal controls (n = 13). Platelet PBR density (Bmax) and the dissociation constant (kd) of the receptor did not differ in the patients when compared with normal controls. Furthermore, no correlation was found between Bmax values and the severity of the depression (as measured by the Hamilton Depression Rating Scale and Beck Depression Inventory) as well as with the severity of the anxiety (as measured by the Hamilton Anxiety Rating Scale). It seems that major depression, in contrast to stress and some anxiety disorders, is not associated with alteration of PBR.