Three cases with an anomalous pulmonary-to-systemic collateral vein (levoatriocardinal vein) connecting the left atrium or one of the pulmonary veins to a systemic vein are described. In two of these cases the atrial septum is intact, the left atrioventricular connection is absent (mitral atresia), and the anomalous vein is the escape channel for pulmonary venous return. In the remaining case, a muscular membrane divides the left atrium, separating the pulmonary venous component from the distal component. The collateral vein may be mistaken for the vertical vein that is associated with totally anomalous pulmonary venous connections, but in all our cases the pulmonary veins inserted normally into the left atrium. Cross-sectional echocardiography, including conventional and color flow Doppler mapping, should overcome potential difficulties in diagnosis.