Hyperprolactinemia can successfully be treated by dopaminagonists such as bromocriptin or lisuride. About 10% of patients complain about side effects like orthostatic hypotension, nausea or vomiting, which may lead to discontinuation of treatment. We therefore conducted a study using terguride--a new dopaminagonist--in 5 patients with hyperprolactinemia and intolerable side effects under conventional treatment. Terguride is the transdihydroderivative of lisuride (Dopergin). We treated 5 patients, 2 men with macroprolactinoma and 3 women with microprolactinoma with terguride. The mean duration of treatment was 15.6 months (7-37 months). Patients were treated with up to 5 mg terguride daily. All 5 patients had a marked initial decrease of elevated prolactin levels 8 h after administration of 0.25 mg terguride orally. Three patients became normoprolactinemic after sufficient increase of the dose of terguride, 2 female patients with a microprolactinoma got eumenorrhoeic thereafter. The treatment with terguride was tolerated without side effects by all patients. There were no significant changes of the examined parameters of clinical chemistry nor the other pituitary hormones. Results of cranial computertomography did not change in 4 patients, one patient had tumor progression. Tergurid as a dopaminagonist is an effective inhibitor of prolactin with little side effects and thus a useful drug in the treatment of hyperprolactinemia.