Eleven patients (6 men, 5 women, mean age 42 [25-65] years) with prolactinomas were treated for 4-16 months with a new dopamine agonist (CV 205-502), at a daily dose of between 0.075 and 0.45 mg. All patients had previously undergone surgery and/or been treated with bromocriptine or lisuride, but had not tolerated this therapy well, and/or had not shown sufficient suppression of serum prolactin levels. Baseline prolactin levels were between 149 and 4120 ng/ml. During treatment, levels fell significantly in all patients, to between 2.0 and 683 ng/ml, and to within the reference range in five patients. In seven patients, the adenoma size decreased by 10 to greater than 50%. Adverse reactions were less frequent and less marked than with the prior therapy. The new dopamine agonist is an alternative treatment for prolactinomas where other therapies have been unsuccessful.