The novel hydrophilic sulfoammonium zwitterionic polyethylene glycol (SAPEG) macromolecule was designed and synthesized using polyethylene glycol (PEG, M(w) = 1000) as the starting agent. The sulfoammonium zwitterionic PEG was grafted onto polycarbonate urethane (PCU) via two ways: (1) direct grafting of SAPEG onto PCU using diisocyanate as a spacer; (2) grafting of PEG mono(N,N-dimethyl glycine)ester (APEG) onto the PCU with diisocyanate, and then reacting with 1,3-propanesulfone via ring-opening reaction to form sulfoammonium zwitterionic structure. The X-ray photoelectron spectroscopy (XPS) was used to analyze the elements of the grafted materials. The results showed that the sulfur contents on the modified PCU were 0.5 and 0.9% for both grafting methods, respectively, indicating sulfoammonium zwitterionic PEG has successfully been grafted onto PCU chains. The low-water contact angle showed that the modified PCUs were higher hydrophilic than unmodified PCU. The results of hemolysis test and cytotoxicity test indicated that blood compatibility of the modified PCU was better than that of the unmodified PCU. The modified PCUs are preferred candidates for blood-contacting implants or devices due to the hemocompatibility and nontoxicity in vitro. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 1084-1091, 2011