1,3-dichloro-tetra-n-butyl-distannoxane, which contains Sn-Cl bonds, was used as a novel initiator for atom transfer radical polymerization of styrene in bulk. Some interesting results that were thought to be related to the characteristics of the 1,3-dihalotetra-alkyl-distannoxanes had been obtained. The concentration of the 1,3-dichlorotetra-n-butyl-distannoxane in the bulk solution of styrene was confirmed to be an important factor for the different results of the polymerization. The corrected theoretical molecular weights, which were based on the proposed mechanism, accorded with the GPC results very well. (c) 2007 Wiley Periodicals, Inc.