Poly[2-(methacryloyloxy)ethyl phosphoryleholine]s (PMPCs) with one pendant cholesteryl moiety at the polymer end (PMPC-Chol-I and PMPC-Chol-II) and two pendant cholesteryl moieties at both polymer ends as terminal groups (PMPC-2Chol-I and PMPC-2Chol-II) were prepared by the radical polymerization of 2-(methacryloyloxy)ethyl phosphorylcholine initiated with 4,4'-azobis[(3-cholesteryl)-4-cyanopentanoate] in the presence of 2-mercaptoethanol or thiocholesterol as chain-transfer reagents, respectively. The self-organization of PMPC-Chol and PMPC-2Chol was analyzed with fluorescence and H-1 NMR measurements. The critical micelle concentrations of PMPC-Chol-I with a degree of polymerization (P-n) of 91 and of PMPC-2Chol-I with a P-n value of 165 were 250 and 27 mg L-1, respectively. The blood compatibility of PMPC-2Chol was evaluated from the Michaelis constant (K-m) for the enzymatic reaction of thrombin and a synthetic substrate, S-2238, in the presence of PMPC-2Chol. K-m was 0.07, 0.05, and 0.56 for PMPC-2Chol-I with P-n = 165, PMPC-2Chol-II with P-n = 38, and PMPC (an intrinsic viscosity of 0.54 dL g(-1)) initiated with 2,2'-azobisisobutyronnitrile in the absence of chain transfer agent, respectively. A mixture of PMPC-2Chol-II and cholesterol as a drug. model formed a lamellar type of complex with an interplanar spacing of d = -35.2 Angstrom. (C) 2003 Wiley Periodicals, Inc.