1. Hyperprolactinemia was found in 73 out of 445 patients as the underlying cause of primary or secondary amenorrhea, There was only in 65 cases both amenorrhea and galactorrhea. 2. Pituitary tumors were found in 21 cases. The causes of hyperprolactinemia in the other patients remained unclear. 3. Concentration of LH and FSH in serum was normal or lowered. Stimulation of LH and FSH by LHRH was possible only in part. 4. Regardless of the cause of hyperprolactinemia in all patients hPRL-levels were lowered significantly by 2.5 mg CB 154 within 4 hours. 5. Longtime suppression of hPRL by CB 154 normalized LH- and FSH- concentrations in serum and its response to LHRH. 6. Ovulatory cycles were observed in all cases treated by CB 154 (N = 25), 11 patients became pregnant.