A new method for chemically cross-linking polysilastyrene using divinylbenzene as the cross-linking agent is reported. The procedure involves a single-step synthesis using the alkali-metal sodium to promote the polymerization of dimethyl-dichlorsilane in the presence of the comonomers phenylmethyl-dichlorosilane and divinylbenzene. The cross-linked polymer can be readily converted to beta-SiC on pyrolysis at 1500degreesC. The beta-SiC obtained by this procedure is nanocrystalline and has a grain-size distribution of 8-20 nm.