One hundred seventy adult patients with possible congenital or valvular heart disease underwent contrast two-dimensional echocardiographic examination as part of a precatheterization evaluation. Persistent left superior vena cava was detected in 5 patients, each of whom demonstrated an abnormally large coronary sinus. Injection of echocardiographic contrast material from a peripheral left arm vein resulted in early opacification of this structure before other right-side chambers, thus suggesting abnormal venous drainage. Persistent left superior vena cava was confirmed in all 5 patients at the time of catheterization and/or surgery.