Stereotactic thermocoagulative lesions of the subthalamic nucleus (STN) have been shown to induce significant motor improvement in patients with Parkinson’s disease (PD). We report 89 PD patient treated with unilateral subthalamotomy . Sixty-eight patients were available for evaluations after 12 months, 36 at 24 months and 25 at 36 months. The UPDRS-motor (Unified Parkinson’s Disease Rating Scale) scores significantly improved contralaterally to the lesion in the “off” and “on” states throughout the follow-up, except for the “on” state at last evaluation. Axial features and signs ipsilateral to the lesion progressed steadily throughout the study. Levodopa daily doses were significantly reduced by 45, 36 and 28% at 12, 24 and 36 months post-surgery. Fourteen patients (15 %) developed post-operative hemichorea-ballism which required pallidotomy in 8. These 14 patients had significantly higher dyskinesia scores (levodopa-induced) pre-operatively than the entire cohort. We conclude that unilateral subthalamotomy is associated with significant and sustained motor benefit contralateral to the lesion. Further work is needed to ascertain what factors led to severe, persistent chorea-ballism in a subset of patients. Subthalamotomy may be considered an option in circumstances when Deep Brain Stimulation is not viable.