In two patients with Parkinson's disease and L-Dopa induced dyskinesia we administered morphine orally to alleviate lumboradicular pain unresponsive to any other form of treatment. Besides an alleviation of the pain both patients showed a decrease in dyskinetic movements at very low doses of morphine and an increase in akinesia at higher doses. This observation indicates a modulation of basal ganglia output by morphine with the possibility of reducing L-Dopa induced dyskinesia in patients treated with morphine for pain.