It is the purpose of this report to present findings on the immediate and longe-range postoperative intellectual functioning of a large series of patients who underwent chemopallidectomy and Chemothalamectomy1-6for the relief of Parkinsonian symptoms. The findings are based on the Wechsler-Bellevue Intelligence Scale, Form I. Background The following review of the literature on the intellectual effects of brain injury, disease, and surgery will emphasize, particularly, those utilizing the Wechsler-Bellevue Scale. Allen, in a series of studies on both the brain-injured and the brain-diseased,7-10concludes that both groups demonstrate “a depressed level of efficiency” in intellectual functioning, faring more poorly on performance items than on verbal ones. Their primary handicap is in the area of motor manipulation. Most resistant to organic inroads were the subtests of information, comprehension, and vocabulary. Other Wechsler studies on the organically impaired report like findings. Goldman et al.