A variety of chemical treatments were applied to standard clinical nonvelour and new velour polyester vascular grafts. Silver-allantoin-heparin (SAH) complex treatment inhibited four species of bacterial growth in vitro, and significantly protected the graft from bacteremia of 50,000 Staphylococcus aureus in vivo. At six to eight months, superior vena caval replacement in 62 dogs demonstrated a nonvelour control patency rate of 67% (ten of 15) and 93% (14 of 15) for similar grafts treated with SAH. The most compliant grafts with the thinnest outer capsules and pseudointimas at six to eight months were those treated with SAH. It is concluded that standard clinical polyester grafts treated with the SAH complex have a bacteriostatic surface both in vitro and in vivo. Additionally, such treatment is not thrombogenic and yields a favorable long-term tissue response to prosthesis.