For one of the approaches to antithrombogenic materials, the combination of synthetic polymers with physiologically active substances seems to be promising. One of these ways involves crosslinked urokinase (HM-UK), in which urokinases are linked with side chains of poly(2-hydroxyethyl methacrylate) (PHEMA) by 4,4′-diisocyanatodiphenyl-methane, and encapsulated urokinase (HMe-UK), in which urokinases are encapsulated in the network of crosslinked PHEMA. The HMe-UK with a low degree of crosslinking was found to be highly antithrombogenic. For another way, Val-Pro-Arg-immobilized polyetherurethaneurea (PEUU) was synthesized. The tripeptide, Val-Pro-Arg, is a substrate of thrombin. The tripeptide-immobilized PEUU was found to complex specifically with thrombin and inactivate it, and hence to prolong the thrombin time and the active partial thromboplastin time. For a further approach to antithrombogenic materials, the design of materials which are covered with a living tissue formed by cell proliferation seems to be promising. For one of the ways in this approach, Arg-Gly-Asp-Ser-immobilized silicone films were synthesized. The tetrapeptide constitutes the active site of cell-adhesion proteins. A number of fibroblast cells were found to grow on the tetrapeptide-immobilized silicone film more resistant to changes of temperature and pH than proteins. Third, novel functions such as cell separation are expected, according to the nature of the carrier macromolecule.