The study describes the effects of ACTH, prolactin and other protein hormones on the synthesis and secretion of steroid hormones by tissue from a feminising adrenocortical carcinoma removed from a post-menopausal female. Steroid production by the tissue was determined by high resolution-mass fragmentography and by radioimmunoassay. Prolactin and ACTH stimulated the synthesis of estrogens by the tissue whereas GH, LH and ACTH were more effective than prolactin in stimulating androgen synthesis. The effect of protein hormones, other than ACTH, on adenylate cyclase activity of this tumour tissue indicated a lack of specificity of the membrane receptor sites.