Treatment of (4-bromophenyl)diethoxymethylsilane with magnesium in THF gave poly[p-(ethoxymethylsilylene)phenylene] (1a) in 58% yield. Similar reactions of (4-bromophenyl)triethoxysilane and (3-bromophenyl)diethoxymethylsilane with magnesium afforded poly[p-(diethoxysilylene)phenylene] (1b) and poly[m-(ethoxymethylsilylene)phenylene] (1c) in 61% and 27% yields, respectively. The Si-OEt bonds of polymer 1a could be readily transformed into the Si-Cl bonds, by treating the polymer with excess acetyl chloride, while polymer 1b did not react with acetyl chloride. Treatment of polymers 1a-c with lithium aluminum hydride produced the respective polymers having an Si-H bond. The polymers having an Si-OEt and Si-Cl bond readily reacted with a variety of nucleophiles, including Grignard reagents and organolithium reagents, to afford substitution products. The thermal properties of the polymers thus obtained were investigated by thermogravimetric analysis in a nitrogen atmosphere.