A novel polyurethane iniferter, synthesized from equal moles of toluene diisocyanate and 1,1,2,2-tetraphenyl-1,2-ethanediol, was used to polymerize acrylonitrile to assess whether it proceeded via a "living" radical polymerization mechanism. From the kinetic results, the rate of polymerization could be expressed as R(p) alpha [BpT](0.98)[AN](1.64). The increase of number-average molecular weight with increase of both conversion and polymerization time, the bimodal molecular weight distribution in gel permeation chromatography and the increase of molecular weight in the post-polymerization of polyacrylonitrile confirm that the present tetraphenylethane-based polyurethane iniferter follows a "living" radical polymerization mechanism.