To determine their perioperative risk, we reviewed the records of 35 patients with hypertrophic cardiomyopathy diagnosed by cardiac ultrasound and/or catheterization who underwent general (52) or spinal (four) anesthesia—a total of 56 major surgical procedures. There were no operative or related perioperative deaths and no significant ventricular tachyarrhythmias. Intraoperative or postoperative complications included: myocardial infarction with heart failure in one patient who also had coronary artery disease and was one of three patients who had spinal anesthesia, arrhythmia requiring therapy in eight, and angina during supraventricular tachycardia in one. We conclude that the risk of general anesthesia and major noncardiac surgery is low in patients with hypertrophic obstructive cardiomyopathy. Spinal anesthesia, which decreases systemic vascular resistance and increases capacitance, may be relatively contraindicated. Concomitant coronary artery disease may increase the risk.