In this study we claimed to observe the variations of alfa motor neuron excitability, espacially during the fonctional phase of central nervous system. Twenty patients from Parkinson polyclinic of Ankara State hospital and eleven volenteers are included. The H-Reflex recovery ratıos (HRRR) of the parkinson patients were significant comparedto the control group. The difference of H-Reflex recovery curves between group1 and group2 were not sinificant. The most importent percentage variations were during 200msec and 600msec interstimulus intervals in IV. and V. phase subsequently.