A minority of patients with obsessive-compulsive disorder (OCD) have a chronic course and extreme disability, with symptoms refractory to pharmacological and psychological treatment. Considerable uncontrolled evidence suggests such cases may respond to neurosurgical intervention. The authors update current stereotactic procedures and their efficacy, safety, and side effect profiles. The design of an ongoing placebo-controlled trial of Gamma Knife capsulotomy for refractory OCD is outlined. Drug treatment of OCD may be assumed to affect a proposed functional imbalance between the frontal lobes and other parts of the brain. As for neurosurgical treatments, both the effects and side effects may be viewed as expressions of their influence on this functional imbalance.