The progress of 50 previously untreated patients with idiopathic Parkinson's disease taking maximum tolerated doses of bromocriptine is compared with patients who had taken levodopa. Twenty-eight of the bromocriptine treated patients showed sustained benefit for at least one year and in five this persisted longer than five years. Fewer of the late complications of levodopa therapy occurred in those taking bromocriptine; drug-induced dyskinesia was seen in only one patient and oscillations in performance were not observed. There was a tendency for deterioration to develop after two years treatment when patients then failed to respond well to levodopa. It was not possible to extend the period of effective control of disabilities by first giving bromocriptine.