Methods for coating a prosthetic surface with anti-thrombogenic, or anti-coagulant, proteins are disclosed. The methods involve contacting a surface of a prosthetic material with a composition containing multimers of fibrin degradation products. These multimers, preferably D-dimers, have cross-linked D-domains. The methods of the invention are useful for providing an anti-thrombogenic coating on prosthetic implants which are exposed to a patient's blood after implantation, for example vascular grafts and artificial heart valves.