Noncompaction of the left ventricular myocardium is a rare congenital disorder characterized by the presence of numerous prominent trabeculations and intertrabecular recesses in the left ventricle. Clinical manifestations vary from no symptoms to congestive heart failure, arrhythmias, and thromboemboli. We report a case in which asymptomatic noncompaction of the left ventricular myocardium was considered likely. The patient was a previously healthy 31-year-old woman who presented with gross hematuria and was admitted to our hospital for renal biopsy. Perioperative echocardiograms demonstrated thinning and hypokinesis in the left ventricular inferior wall. Spongiform trabeculations were found in the inferior and posterior wall, and color flow Doppler studies confirmed the presence of blood flow within them. Cine magnetic resonance imaging showed prominent trabeculations and deep intertrabecular recesses. These findings were consistent with isolated noncompaction of the left ventricular myocardium. The patient has been asymptomatic and presented no major complications during 4 years of follow-up. Isolated noncompaction of the left ventricular myocardium is a cardiomyopathy that is more prevalent than previously reported. Combined echocardiographic and magnetic resonance imaging findings are important in the diagnosis of this entity. Because of the relatively high incidence of congestive heart failure, arrhythmias, and thromboemboli, their early diagnosis is important.