The incidence of venous insufficiency is increasing, approximately 800,000 new cases are reported yearly in the United States. Medical treatment of venous insufficiency syndrome has been associated with a high incidence of failure. Although vein valve transplantation has resulted in improvement in the majority of cases, late degeneration and incompetency of the valve prompted us to devise a prosthetic vein valve for experimental use. Ten dogs underwent insertion of a prosthetic vein valve without anticoagulants. Between 3 and 8 months after insertion, ascending and descending venography revealed patency and competency of these valves.