Ten patients with clinical, laboratory and radiographic evidence compatible with the diagnosis of prolactinoma were treated with two dopamine agonists. One group (N = 6) took bromocriptine and the other group (N = 4) used pergolide, a longer-acting agent. Both medications were found to reduce prolactin levels significantly from baseline, but an oscillatory pattern with significant fluctuation was seen in the mean prolactin levels in the patients taking bromocriptine. Three patients did not achieve euprolactinemia on bromocriptine, 2.5 mg qid, the maximum dose used in this study. All of the study group taking pergolide became euprolactinemic rapidly; no more than a single dose of 100 micrograms/day was required. Tumor reduction was noted in two patients taking bromocriptine and two taking pergolide. The duration of side effects was shorter and compliance was improved on pergolide therapy.