Twenty-five patients with cirrhosis with a peritoneojugular (LeVeen) shunt had recurrence of ascites because of obstruction of the venous catheter. They were investigated by direct shuntography and angiography of the superior vena cava (SVC). Shuntograms were suggestive of venous obstruction in all patients and showed either complete blockage at the tip of the venous catheter (87%) or partial obstruction (13%). Cavography disclosed a complete obstruction of the SVC or one of its branches in 65% of the patients, a nonobstructive mural thrombus in 17.5%, and sheathing around the catheter in another 17.5%. Blood clots formed at the tip of the catheter and not at its entrance into the vein. Replacement of the venous tubing or a contralateral shunt was successful in only one of eight patients with incomplete obstruction of the SVC. Failure was always due to recurrent venous obstruction. In patients with complete occlusion of the SVC, portal systemic shunts (12 patients) or peritoneosaphenous shunts (two patients) were always successful. These results suggest: that obstruction of the venous tubing of a LeVeen shunt is chiefly caused by the formation of a clot at the outlet of the tubing and that local procedures are prone to failure. Improvement of the long-term results of peritoneojugular shunting in intractable ascites of cirrhosis is clearly dependent on improvement of the venous tubing to decrease its thrombogenicity.