Ropinirole is a novel, non-ergoline dopamine agonist chemical name with a very high specificity for dopamine D2-like receptors, currently being investigated for the symptomatic treatment of Parkinson's disease. The efficacy of ropinirole has been investigated in three placebo-controlled studies: one using ropinirole as monotherapy in early Parkinson's disease and two using it as an adjunct to L-dopa in patients who are experiencing fluctuations in motor response. Ropinirole therapy for 12 weeks was an effective symptomatic therapy in both patient groups, as measured by either a significant improvement in the motor score of the UPDRS, reduction of awake time spent "off" or a reduction in the dose of L-dopa. Ropinirole therapy was generally well tolerated, the most frequent adverse events being nausea and vomiting which are typical of all dopamine agonists, but unlike other dopamine agonists, CNS side-effects were of the same magnitude as found patients receiving placebo.