The effect of Ergobromocriptine treatment on serum testosterone and prolactin levels in 15 patients with prostatic carcinoma and 15 patients with benign prostatic hyperplasia was examined. The prolactin levels which were elevated in patients with prostatic carcinoma showed a significant decrease after suppression with Ergobromocriptine. The selective effect of Ergobromocriptine on prolactin levels of patients with prostatic carcinoma may control the progression of the disease.