The effects of single oral doses of 0.1 mg lisuride hydrogen maleate (lisuride), a semisynthetic ergot derivative given at 09.00 h, on the serum levels of prolactin (PRL), luteinizing hormone (LH), follicle-stimulating hormone (FSH), growth hormone (GH), thyroid-stimulating hormone (TSH), oestradiol and cortisol were studied in six normally cycling women and six patients with hyperprolactinaemic amenorrhoea. The same subjects received placebo and the results were compared with those of lisuride. Within 1 h after oral administration of lisuride, PRL levels decreased significantly (P less than 0.05) and reached the lowest level at 4 h after ingestion and stayed low until 8 h in both normal women and hyperprolactinaemic patients. LH levels slightly but not significantly decreased after lisuride administration in hyperprolactinaemic patients. Serum cortisol levels increased at 13.00 h, probably due to the effect of meal. No significant differences between the lisuride group and placebo group were observed in GH, TSH, FSH and oestradiol levels. These results suggest that lisuride acts as a long-acting prolactin suppressor and that it has little effects on the secretion of other pituitary hormones. Therefore, this drug could be useful for treatment of hyperprolactinaemic patients.