Atrial fibrillation is commonly observed in patients with hypertrophic obstructive cardiomyopathy. Episodes of paroxysmal atrial fibrillation are often torturous and limit the quality of life by causing congestive heart failure, transient hypotension, or bradycardia. Control of paroxysmal atrial fibrillation in patients with hypertrophic obstructive cardiomyopathy is considered to be important for symptomatic improvement and prevention of the development to chronic atrial fibrillation. The authors report on 3 patients with hypertrophic obstructive cardiomyopathy who suffered from paroxysmal atrial fibrillation despite receiving medical treatment using antiarrhythmic agents. However, after undergoing percutaneous transluminal septal myocardial ablation, the incidence of episodes became significantly less frequent. Percutaneous transluminal septal myocardial ablation is normally performed for attenuating left ventricular obstruction by reducing the systolic anterior motion of the mitral leaflet. However, in these patients, this procedure was also effective in preventing supraventricular arrhythmia, probably by improving left ventricular diastolic dysfunction, smooth blood inflow into the left ventricular, and decreasing the pressure stress against the left atrial wall.