The tricuspid valve is left-sided in congenitally corrected transposition of the great arteries and other cardiac malformations in which the ventricles are inverted. In an anatomical study of 20 hearts with ventricular inversion, nine were found to have Ebstein's anomaly of the left-sided tricuspid valve. These included eight with congenitally corrected transposition of the great arteries and one with a double outlet inverted right ventricle. Pathoanatomically left-sided Ebstein's anomaly differed from the classic right-sided variety in several respects: 1) the atrioventricular sulcus circumference was not increased; 2) the anterior leaflet of the valve was frequently cleft; 3) the anterior leaflet may interfere with the ventricular outflow; 4) the ventricular cavity receiving the malformed tricuspid valve was small, rather than dilated--and in congenitally corrected transposition of the great arteries, this is the systemic ventricle connected to the aorta. Significant hemodynamic dysfunction of the left-sided tricuspid valve has been reported in a high proportion of cases of congenitally corrected transposition of the great arteries, and surgical repair of the valve may be necessary. Our study suggests that surgical procedures used in classic right-sided Ebstein's anomaly, such as valve plication and annuloplasty or valve replacement with a high profile prosthesis, are not suited to the pathoanatomy of left-sided Ebstein's anomaly.