To study correlation between brain rhythm and tremor rhythm. 37 patients having paralysis agitans were examined by means of the electroencephalogram and the electromyo-gram; the records being taken simultaneously on a 2-channel ink-writing oscillograph. When artifact, caused by a shaking of the head, was eliminated, no correlation between these 2 rhythms was found. Furthermore, in a number of these patients, the tremor rate varied in 2 extremities, and even in muscles of the same extremities. The rhythm in paralysis agitans apparently does not originate in the cerebral cortex.