One hundred and sixty-five patients with erectile dysfunction were assessed at the Athens Medical Sex Institute: 60 men (36.4%) considered their condition as organic, 52 (31.5%) rated it as mostly psychogenic, 45 (27.2%) thought it could be of mixed aetiology and 8 (4.8%) could not comment at all as to the aetiology. Initial psychologic evaluation rated the condition in the majority of cases as psychogenic (130 patients, 84.8%). No psychologist considered the erectile dysfunction as purely (100%) organic. After the urological and endocrine evaluation, vascular disorder was considered in 30 patients (18.2%), endocrine dysfunction in 16 patients (9.7%) and psychogenic in 109 patients (66.1%). Sixteen of the above patients had definite hyperprolactinaemia, two had large-sized prolactinomas as revealed by magnetic resonance imaging (MRI) and pituitary function tests. Four had nonfunctioning pituitary tumours, which was also based on MRI and pituitary tests. Four had small prolactin (PRL) adenomas. Drug-induced hyperprolactinaemia was suspected in six patients who used medications affecting PRL secretion and had no evidence of tumour on radiological evaluation. In conclusion, hyperprolactinaemia in men with erectile dysfunction needs to be evaluated before considering any other treatment.