Stereotaxic operations were carried out in 96 cases of athetotic cerebral palsy to relieve involuntary movements and muscle hypertonus between 1955 and 1970, of which 43 cases (22 dystonic, 21 tension athetotic) were followed up postoperatively from 6 months to 12 years at the clinic or by questionnare. Many severely disabled patiensts were included in this study and 30 of the 43 cases belonged to Class Ⅳ of the classification of functional capacity of the American Academy for Cerebral Palsy. Ages at operation ranged from 5 to 40 years, and about a half of the patients were 5 to 10 years. Targets of operation included the ventrolateral nucleus of the thalamus (VL), VL plus centromedian nucleus of the thalamus (CM), globus pallidus (GP) and field of Forel H. A total of 79 operations were performed in these 43 cases. Sixteen (11 dystonic, 5 tension athetotic) out of the 43 cases were operated on unilaterally and 27 (11 dystonic, 16 tension athetotic) were operated bilaterally. Concerning the relationshp between targets and postoperative results, both VL and GP lesions were effective on muscle hypertonus. However, VL or VL plus CM lesions produced better effects on both involuntary movements and muscle hypertonus than GP or field of Forel H lesions. Patients who had improvement in voluntary control were limited to those who had good results in both involuntary movements and muscle hypertonus. Dystonic patients generally obtained much better postoperative results than tension athetotic patients. Postoperative courses of bilateral operations were variable and complex. When bilateral operations are attempted, it is desirable that the contralateral operation be performed more than six months after the initial one. Dystonic patients operated on unilaterally maintained excellent postoperative results for a long period. Dystonic patients who were operated on bilaterally also had good surgical results for long periods. However, the long-term results in tension athetotic patients operated on either unilaterally or bilaterally were not as good as those in dystonic patients. Therefore, the dystonic form of cerebral palsy is a good candidate for stereotaxic operation. Complications of the operations were of almost the same frequency in unilateral and bilateral operations. In bilateral operations, the bilateral VL lesion and VL plus CM lesion were the most effective long-term. When motor symptoms recurred, they did so within six months of the operation.