The H-reflex was studied on 27 cases of Parkinsonism, including 8 cases of hemiparkinsonism. 1. The fluctuation of H-reflex amplitude was more unstable on the parkinsonism, comparing with normal subject. 2. On the hemiparkinsonism, the fluctuation of H-reflex amplitude in nonaffected side showed interest character. The fluctuation was in the normal level at tremor-rest stadium in the affected side, abnormally increased level at tremor stadium in the affected side. 3. The fluctuation of H-reflex amplitude was considered to be influenced by the descending impulses from the higher level of the central nervous system at the time of tremor.