A link between stressful life events and development or exacerbation of depression has been established via a large body of evidence. An alteration in the regulation of the hypothalamic-pituitary-adrenal (HPA) axis in depression has also been associated with an increase in cortisol secretion. As arginine-vasopressin (AVP) plays an important role in the activation of HPA axis during stress, the present study investigated ACTH and cortisol secretory response induced by an AVPrelated peptide desmopressin (ddAVP) in patients with major depression. Prior to antidepressant treatment, endocrinological parameters were evaluated and correlated with the clinical response to venlafaxine treatment, which offers a dual antidepressant action. Depressive patients with no other psychiatric pathology were evaluated with 17-item Hamilton Depression Scale (HAMD) in order to follow-up the response to venlafaxine. After 1 wk of treatment, 60% of patients reduced their initial HAM-D score to at least 25%; t