L-Dopa is still the most effective drug for the treatment of Parkinson's Disease, but after 5 years or more of therapy fluctuations in motor performance and abnormal involuntary movements commonly appear. Continuous intravenous infusions of L-Dopa abolish or strikingly reduce such fluctuations. Unfortunately, this is not suitable for daily treatment because of the low solubility of L-Dopa. Lisuride is a potent dopamine agonist and is very soluble in water. In this study the clinical effects of L-Dopa and lisuride continuous intravenous infusions were compared in a group of 20 fluctuating parkinsonian patients. L-Dopa controlled fluctuations in almost all the subjects, whereas only seven patients were continuously mobile while taking lisuride. Another seven patients showed a fluctuating response and the remaining six did not satisfactorily respond to lisuride. Dyskinesias were present in all patients during "on" phases, with both levodopa and lisuride treatment.