The neurosurgical treatment of Parkinson's disease (paralysis agitans) had its beginning in the 1930's. At that time, Bucy4 and Klemme11 demonstrated that ablation of the motor and premotor cortex in patients with parkinsonism resulted in improvement in tremor and rigidity. While the operative mortality and morbidity were considerable and the long-term results generally unimpressive, it is noteworthy that occasionally rigidity and tremor could be significantly decreased with little persistent weakness or spasticity. One of us (C. H. M.) has seen two cases of postencephalitic Parkinson's disease with persistent improvement in rigidity and tremor and with only slight reflex preponderance contralateral to cortical excision done by Klemme over 20 years before. Other approaches to the surgical treatment of Parkinson's disease included partial spinal cord pyramidal tract resection by Putnam,19 mesencephalic pedunculotomy by Guiot and Pecker,10 Meyers' excision of the head of the caudate nucleus and section of