Several problems arise when polymeric materials are placed in the body: (1) damage to the body such as blood coagulation, hemolysis, and protein denaturation, and (2) degradation of the polymers caused by exposure to the body's enzyme system. Several methods are presented in this paper to produce elastomeric materials that do not cause clotting of blood. This is accomplished by chemically binding a mucopolysaccharide (heparin) to their surfaces. The materials that have been treated in the work are silicone rubber, polyester polyurethan rubber, natural rubber, and butadiene pyridine rubber.