Pergolide, an experimental dopamine agonist, was administered to 56 patients with advanced Parkinson disease who were no longer satisfactorily responding to levodopa, including 45 patients with diurnal oscillations in performance: “on-off” phenomena. Lisuride, an experimental dopamine agonist was administered to 63 patients with advanced Parkinson disease. Pergolide or lisuride, when added to levodopa, resulted in a significant decrease in disability in both the “on” and the “off” period, and an increase in the number of hours in which patients were “on”. Forty-one of 56 patients (73%) improved on Pergolide. Thirty-seven of 63 patients (59%) improved on lisuride. Mean dose of pergolide was 2.5mg. (range 0.2 to 10.0mg.). Mean dose of lisuride was 2.6mg. (range 0.2 to 5.0mg.). Pergolide was discontinued in 18 patients because of adverse effects, including an organic confusional syndrome (six patients), dyskinesias (four patients) and cardiovascular abnormalities (three patients). Lisuride was discontinued in 26 patients because of adverse effects, including an organic confusional syndrome (15 patients), dyskinesias (five patients) and vasospasm (two patients). Pergolide was discontinued in nine patients and lisuride in 12 because of a lack of effect or a declining effect. Both drugs are equally useful in patients with advanced Parkinson disease.