The blood compatibility has been studied for block copoly (dimethylsiloxane-γ-benzyl-L-glutamate) which was synthesized by reacting primary amine-terminated living polydimethylsiloxane with N-carboxy anhydrides of γ-benzy1-L-glutamate. The living polydimethylsiloxane was prepared by polymerization of hexamethylcyclotrisiloxane (D₂) using n-butyllithium as initiator in toluene, And primary amine-terminated silicone was obtained from react ing living polydimelhylsiloxane with γ-aminopropyltriethoxysilane. The blood compatibility of block copolymer was estimated in comparison with silicone, PBLG, and blendmer of PBLG/silicone by passing truman blood through polymer precoated glass beads column. The behavior of platelet on tile polymer surfaces was investigated by scanning electron microscopy and average number of fluted platelets was also measured.