22 patients with metastatic carcinoma of the prostate were treated by subcapsular orchidectomy and followed by regular determinations of plasma testosterone, dihydrotestosterone, Δ4-androstenedione, dehydroepiandrosterone sulfate and testosterone estradiol-binding globulin as well as salivary testosterone, which reflects free plasma testosterone. Subcapsular orchidectomy constantly induced a dramatic and stable decrease in testicular androgens without modification of adrenal androgens or testosterone estradiol-binding globulin. Free testosterone levels vary widely for a given value of plasma testosterone, probably due to individual variations of testosterone estradiol-binding globulin. Salivary testosterone is preferable to plasma testosterone for monitoring hormonal therapy for metastatic carcinoma of the prostate. In another group of orchidectomized stage-D(2) patients, obstructive symptoms motivated transurethral resection of the prostate allowing the assay of intraprostatic dihydrotestosterone which was constantly below the dihydrotestosterone level of androgen-independent tissues (below 2.5 ng/g).