To identify the incidence of left heart abnormalities in patients with Ebstein anomaly, recognizing that left-sided lesions in this patient group have been overlooked. According to the echocardiography database at the Mayo Clinic in Rochester, Minn, 106 consecutive patients with Ebstein anomaly underwent echocardiography between July 1, 2001, and February 28, 2003. Clinical data as well as electrocardiographic and echocardiographic reports and images were reviewed. Ebstein anomaly was severe in 76 patients (72%). Previous tricuspid valve surgery was reported in 46 patients (43%), and previous closure of an atrial septal defect or patent foramen ovale was reported in 34 patients (32%). Left ventricular (LV) myocardial changes resembling noncompaction occurred in 19 patients (17.9%), LV systolic dysfunction in 7 patients (7%), LV diastolic dysfunction in 34 (36%) of 95 patients, and LV dilatation in 4 patients (4%). Additional left-sided cardiac lesions included mitral valve prolapse in 16 patients (15%), bicuspid aortic valve in 8 (8%), mitral valve dysplasia in 4 (4%), and ventricular septal defect in 8 (8%). Wolff-Parkinson-White syndrome occurred in 22 patients (21%). The QRS axis tended to be different in LV noncompaction with a mean +/- SD axis of 12 degrees +/- 74 degrees vs 36 degrees +/- 66 degrees overall (P=.08). Otherwise, there were no differences in clinical or surgical data between the groups with normal and abnormal LV myocardium. In patients with Ebstein anomaly, left heart abnormalities involving the myocardium or valves were observed in 39% of patients. Ebstein anomaly should not be regarded as a disease confined to the right side of the heart.