A 25-year-old woman presented with an extensive adrenocortical carcinoma with severe virilization and mild Cushing's syndrome. In the tumour there was a primacy of the P450C17 (17,20-lyase) over the P450C21 (21-hydroxylase) route, favouring the synthesis of androgens over corticoids. Preoperatively, the patient was treated with the antimycotic agent ketoconazole, a known inhibitor of steroid synthesis, at a dose of 600 mg/day and after a week 1200 mg/day, to reduce operation risks and to achieve a better metabolic control. This treatment markedly decreased hyperandrogenism and normalized the hypercortisolism. The main effect of ketoconazole was at the 17,20-lyase level and probably at a locus prior in steroidogenesis, i.e. at the P450SCC and/or 17 alpha-hydroxylase level. In contrast with other studies no effect at all was seen on the 11-hydroxylase activity of P450C11. After removal of a massive adrenal carcinoma, extending into the vena cava, vena cava resection and hemihepatectomy because of liver invasion, plasma cortisol and androgen values normalized. Despite adjuvant chemotherapy with o,p'-dichlor-diphenyl-dichloretan (4000 mg daily) hyperandrogenism soon recurred and lung metastases became manifest. Within 2 months after starting combined chemotherapy with 5-fluorouracil, cisplatin, and doxorubicin lung metastases almost completely disappeared with clinical and biochemical resolution of the hyperandrogenic state.