In 1909 Horsley1described a method of excision of an area of motor cortex for the relief of violent athetoid and convulsive movements of an upper extremity. This consisted in splitting the pia lengthwise over the center of the convolution to be partially excised, gradually pushing the pia back to the extreme edge of the sulcus on either side, and then removing the necessary amount of the convolution. In 1935 Sachs2reported experiences with this subpial resection of the cortex in the treatment of focal epilepsy and athetosis. The actual procedure he called the Horsley operation. Since that time there have been other cases in which it was thought that the procedure was indicated and, having found it to be of definite value, I am making this report. In the paper2mentioned, eleven cases in which this operation had been done were reported. Two of the patients