Free radical reactions with hexamethyldisilane were investigated. In carbon tetrachloride, di-tert-butyl peroxide- or benzoyl peroxide-catalyzed reactions of hexamethyldisilane give rise to the formation mainly of (chloromethyl)pentamethyldisilane. The results are interpreted in terms of an intermediate (pentamethyldisilanyl)methyl radical which abstracts a chlorine atom from the solvents. Without solvent, the (petamethyldisilanyl)methyl radical affords the dimerized product, 1,2-bis(pentamethyldisilanyl)ethane. Alternative preparations for the latter compound are also recorded. In these cases, no rearrangement product, trimethyl[(dimethylsilyl)methyl]silane, which was observed at pyrolysis of hexamethyldisilane, was obtained.