Abstract A sensitive animal model was used to investigate treatment designed to improve vascular graft patency. A Dacron graft was inserted into the infrarenal vena cava of 30 rabbits. Half were treated with subcutaneous Arvin for 28 days after operation. This produced a significant lowering of the postoperative plasma fibrinogen. The patency rate of the grafts in the treated rabbits was significantly greater than in the control rabbits.