Twenty-four parkinsonian patients compared pergolide and bromocriptine therapy in a randomized double-blind, two-period crossover study. Both drugs were adjusted to an optimal balance between benefits and side effects. The mean daily dose and dose range for pergolide and bromocriptine were 3.3 mg (0.7 to 7.2) and 42.7 mg (5.8 to 87.5), respectively. Adjunctive medications, which for most patients included levodopa (plus carbidopa), were not altered during the study. A similar spectrum of clinical effects was found with both drugs and with lisuride, which was used to treat 13 of the patients in a previous study. Despite neurochemical differences in the antiparkinsonian ergots, their clinical utility is quite similar. We draw attention to hepatotoxicity and pleural reactions that may occur rarely with these drugs.