The photopolymerization of methyl methacrylate (MMA) with bis(cyclopentadienyl)titanium dichloride (Cp2TiCl2) in a H2O-MeOH [1 : 1 (v/v)] mixture was examined at 40 degreesC in the presence of 2,2'-bipyridyl (Bipy), 1,10-phenanthlorine (Phen) or sparteine (Spr) as the chelating reagent. The presence of these chelating reagents retarded the photopolymerization. Poly(MMA)s formed in the presence of them were found to contain a considerable fraction of the benzene-insoluble part, in contrast to the ones in the absence of them. Spr was the most effective for formation of the insoluble part. The benzene-insoluble poly(MMA) was insoluble in usual organic solvents including acetone, tetrahydrofuran, ethyl acetate, and dimethyl sulfoxide, suggesting crosslinking. However, poly(MMA) reproduced by hydrolysis of the insoluble part followed by methylation was soluble in usual organic solvents, indicating no crosslinking between polymer main chains. The insoluble part was thermally more stable than the soluble part. Polymerization of ethyl methacrylate in the presence of Spr gave similar results.