Numerous diagnostic pitfalls were noted among 6 infants with infradiaphragmatic total anomalous pulmonary venous drainage, including prolonged moderate respiratory distress in 2 infants, normal cardiac examination in 2, normal electrocardiograms in 2, arterial PO2 in excess of 100 torr in 3 cases, right radial/umbilical arterial PO2 gradients consistent with significant right-to-left ductal shunting in 2 of 4 cases, misleading M-mode echocardiography in 2 of 4 cases, and missed diagnosis at initial cardiac catheterization despite pulmonary angiography in 1 case. Helpful radiographic features included small heart, congested lungs, and pleural effusions in all 6 cases, and visualization of the anomalous trunk overlying the liver on slightly rotated abdominal flat plates in both cases so examined. Bedside umbilical venous catheterization was pathognomonic in 3 cases and suggestive of the diagnosis in the fourth case. Cross-sectional echocardiography was diagnostic in the 1 case in which it was employed. Intraoperative and postoperative pulmonary hypertension led to the demise of the 4 infants who survived long enough to undergo surgery. In addition to early diagnosis, measures to insure maximal decompression of the pulmonary circuit at surgery should improve survival.