1,3-Disilacyclobutanes of the types are prepared (a) by ring synthesis from chloromethylchlorosilanes R1R2Si(CH2Cl)Cl, (b) by thermolysis of monosilacyclobutanes R1R2H2CH2, and (c) by substitution of chlorine with alkyl groups in SiCl-containing 1,3-disilacyclobutanes, obtained by procedures (a) or (b). The compounds have been characterized by analytical and spectroscopic investigations. The synthetic