The results of stereotaxic thalamotomy in 55 cases of dystonia are presented. The 16 cases with generalized dystonia were of varied pathogenesis, only 7 being typical of the idiopathic form of adolescent onset. Four of the 16 cases benefited considerably, but the others showed little or no lasting improvement. These results are in contrast to those obtained by Cooper (1976). Of the 27 cases with segmental or focal dystonia, 22 had spasmodic torticollis; 16 of these had bilateral thalamotomies, and 62 per cent were much improved. The incidence of operative complications, in particular dysarthria, was high following bilateral lesions. The incidence of hemiparesis, known to have persisted for more than a year, was 15 per cent. This complication was as frequent in those with unilateral as with bilateral thalamotomies. The incidence of dysarthria in those without preoperative bulbar dystonia was much higher in those who had bilateral lesions (56 per cent) as compared with those who had unilateral lesions (11 per cent). The group that has been identified as benefiting greatly from stereotaxic surgery comprises those with hemidystonia following unilateral brain damage. In these patients, symptomatic improvement in abnormal movement is striking and the incidence of operative side effects from unilateral lesions is low.