Since it is was first described by James Parkinson in 1817 much has been learnt about Parkinson's disease. The complete picture is not clear, however, and a new impulse has been given to the study of the physiopathology of the basal ganglia by the therapeutic employment of L-Dopa with a peripheral inhibitor of the decarboxylase. This treatment is the best available particularly for akinetic-hypertonic forms. In certain cases, however, patients developed a dyskinetic long-term L-Dopa syndrome, depending on the amount of L-Dopa given and individual sensitivity. The syndrome occurs in Parkinsonism only and can be prevented by thalamolysis. It would appear to be a specific expression of the effect of L-Dopa on the striatonigral system rather than of generic hypersensitivity due to denervation. A personal case is presented.