In 32 subjects with histologically and/or cytologically verified prostatic cancer the hormonal pattern was studied by assaying 18 plasma and urinary hormones or groups of hormones and relating the values to the response to endocrine treatment. Total orchidectomy (orchiepididymectomy) was performed on 9 patients, subcapsular orchidectomy on 13 patients and oestrogen therapy with Estradurin was given in 4 patients. Six patients had total orchidectomy followed by estrogen therapy. With few exceptions all values were within the normal range. The only significant exceptions were the high urinary oestrogen values and the low urinary oestrone + oestradiol/oestriol ratio observed as compared to healthy males working in a factory. No urinary hormone values or ratios of hormone values could be used for the prediction of prognosis in prostatic carcinoma patients. However, the ratios of plasma testosterone/oestradiol (T/Oe2) and testosterone/prolactin (T/Prl) were found to give good information with regard to the response to endocrine treatment. High values for one or both of these ratios meant a good response to treatment in all subjects without exception in this material. Subjects with both ratios low had a good response to endocrine treatment in 50% of the cases. No other plasma hormones measured were of any help prognostically. It is concluded that by measuring the T/Oe2 and T/Prl ratios it seems possible to select a group of patients with favourable primary response to endocrine treatment.