Only limited information is available on which to base the selection of grafts suitable for use in the venous system. Grafting techniques have been applied chiefly to the arterial system, and vein grafts have most frequently been studied from the standpoint of suitability as arterial replacements. Nevertheless, patients are seen in whom a graft to replace or bypass portions of the venous system is desirable. Clinical situations encountered include traumatic laceration of major veins, certain arteriovenous fistulae, facilitation of end-to-side portacaval and splenorenal anastomosis, resection and replacement of the superior mesenteric vein in pancreatectomy for carcinoma, benign and malignant vena caval obstruction, and suggested venous shunts to increase compensation in transposition of the great vessels. This study was undertaken to examine the fate of various types of grafts inserted in the venous system, including fresh autografts, fresh and frozen homografts, and Edwards-Tapp nylon grafts. These grafts were inserted in a