The blood compatibility of S(sulfur)-cyanoethylated keratin(SCEK) was studied. SCEK was obtained by rupture the cystine linkage of wool keratin followed by cyanoethylation. Platelet count, prothrombin time and activated partial thromboplastin time were measured by Coulter counter to investigate the behavior of blood on the surface of SCEK and other four synthetic materials. Enzyme linked immuno sorbent assay was adopted to measure platelet factor IV released from agranule in platelet. The contact an히e and gas permeation rate of SCEK were also measured.