The copolymerization behaviour of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane (DVDS) with styrene in solution, using a free radical initiator, was investigated. Styrene was found to be the more reactive monomer. The FTi.r. and Si-29 n.m.r. spectra indicated that cyclic units were formed from DVDS in the copolymer, with five-and six-membered ring structures being common. The cyclocopolymerization mechanisms and the thermal properties of the cyclocopolymer are reported.