Bis [bis (methylthio) lithiomethyl] dimethylsilane was generated from bis [bis (methylthio) methyl] dimethylsilane by deprotonation with t-BuLi in THF and allowed to react with various dichloro (poly) silanes to give the corresponding 4-to 7-membered polysilacarbacycles in moderate to good yields. The methylthio groups in the cyclized products were readily removed by radical reduction with Bu3SnH.