Diverticula of the left ventricle are rare and only a few cases have been documented in adults. They may be asymptomatic or may present with embolization, pain, endocarditis, or sudden death. We report the case of a 34-year-old woman who presented a cardiac arrest with ventricular fibrillation which required electrical cardioversion. She was found to have a left ventricular diverticulum associated with a subvalvar aortic stenosis. The diverticulum arose from the apex with a narrow connection to the ventricular cavity. A subvalvar fibrous ridge stenosis with a systolic pressure gradient of 115 mmHg was observed. Coronary angiography revealed normal coronary arteries. The diverticulum and the subvalvar fibrous ridge were resected. Histologic examination of the diverticulum wall demonstrated the presence of the three normal layers with marked muscle cell hypertrophy, atypical plexiform structure and fibrous endocardium. The pathophysioloy of diverticula associated with subvalvar aortic stenosis are discussed.