CV 205-502 (octahydrobenzol[g]quinoline), a non-ergot dopamine agonist drug, was administered to 40 patients with hyperprolactinemic syndrome: 16 patients with macroprolactinoma, 14 with microprolactinoma and 10 with non-tumoral hyperprolactinemia. Twenty-four out of 40 patients had previously been treated by surgery and/or bromocriptine, with variable results. All had gonadal dysfunction and 22 patients had galactorrhea. Eight patients with macroprolactinoma had defects of the visual field. Pre-treatment serum PRL levels ranged from 60 to 2050 micrograms/l. The daily dose of CV 205-502 used in this trial ranged from 0.075 to 0.600 mg. After 6-12 months of treatment, serum PRL level decreased in all the patients reaching normoprolactinemia in 31 of them (77.5%) who demonstrated restoration of menses and disappearance of galactorrhea. The remaining nine patients (22.5%) had only a decrease of PRL levels without reaching normoprolactinemia and without any clinical effect. In 12 out of 16 patients with macroprolactinoma not previously surgically treated, a significant tumor shrinkage was shown by means of Computed Tomography and/or Magnetic Resonance Imaging. The disappearance of visual defects was obtained in four out of eight patients. CV 205-502 was tolerated satisfactorily: mild side-effects occurred in four patients in the first week of treatment and spontaneously disappeared, whereas six patients (15%) needed to withdraw the therapy after 6 months because of side-effects. In conclusion CV 205-502 is a potent and well-tolerated drug in the treatment of tumoral and non-tumoral hyperprolactinemic states and is an effective alternative to other dopamine agonists in use today.