We studied whether Parkinson's disease patients who had lost efficacy from pergolide (PERG) could benefit if transferred to bromocriptine (BCT) therapy. Using paired t-tests, we compared motor scores at baseline (when patients were still on PERG) and after 6 months of BCT therapy in 11 patients. No significant improvement occurred in any measure on BCT therapy (mean dose 33.6 mg/day), although patients remained stable. In 6 patients on whom "on/off" data were obtained, decreased "off" time and increased "on" time without chorea occurred, but these changes were not statistically significant. The side effect profile was similar with the 2 drugs.