Angiographic definition of systemic venous connections was obtained prospectively in 780 consecutive patients with congenital heart disease and 102 patients with acquired valvular heart disease undergoing cardiac catheterization. Attempts were made to enter the innomlnate vein and perform a balloon occlusion angiogram in each patient. In patients wlth congenital heart disease, bilateral superior vena cava were present in 3 2 m 1 patients (-4%) wlth levocardia and 319 patients with dextrocardia. Among patients with bilateral superior vena cava (n=35), an innominate vein of variable size that could be entered was present in six patients. Small tributaries connecting the right and left superior vena cava were found and entered in six patients. The superior vena cava was entered via its connection to morphologic left atrium in five patients and via the coronary sinus in 17 patients. Abnormalities of the inferior vena cava were seen in 7/780 patients. The following abnormalities of the inferior vena cava were noted: azygous continuation of rightsided inferior vena cava In levocardia-3 patients, hemiazygos continuation of the leftsided inferior vena cava in levocardi+l patient, azygos continuation of the leftsided inferior vena cava In dextrocardigl patient, interruption of inferior vena cava below the liver with a plexus of veins joining the azygos vein-1 patient, and an inferior vena cava draining into the leftward aspect of the common a t r i u m 1 patient. Abnormalities of the systemic venous connections were seen in 2/102 patients with acquired heart disease: bilateral superior vena cava in 1 patient and bilateral inferior vena cava in 1 patient. Conclusions: Abnormalities of systemic venous connections were seen in . 5% patients with congenital heart disease and 2% patients with acquired heart disease. Small tributaries or an innominate vein of variable size often connect left and right superior vena. Contrast material can be injected into these connections to document the presence of bilateral superior vena cava.