A 48-year-old man with hypertrophic obstructive cardiomyopathy was treated by nonsurgical septal ablation. He had previously received medical treatment using atenolol and verapamil, but severe symptoms of chest discomfort, dyspnea, and shortness of breath had persisted for 2 years. Under coronary angiography control, the first major septal branch of the anterior descending coronary artery was catheterized with a 2.0 mm coaxial percutaneous transluminal coronary angioplasty balloon catheter. After inflation of the balloon, 1.5 ml of absolute alcohol was slowly injected into the septal artery to induce a small septal infarction. The left ventricular outflow pressure gradient was decreased from 108 before to 30 mmHg after the procedure as measured by Doppler echocardiography. His chest symptom improved from New York Heart Association class III to II and left ventricular outflow gradient was maintained at 0 mmHg (at rest) at 3 months after treatment. This is a new, less invasive treatment using catheterization instead of surgical myectomy. The indication, complication, and long-term effect of the treatment must be carefully evaluated, but this is expected to become a useful method.