RhH(CO)(PPh3)(3) appeared to be a very effective catalyst for disproportionation of vinylsilanes and their co-disproportionation with styrene and 1-decene. The insertion of vinylsilane (or bis(silyl)ethene) into the Rh-H bond followed by beta-silyl transfer to form a Rh-Si bond and elimination of ethylene (or vinylsilane), in combination with a MS study of the product of the reaction of styrene-d(8) with vinylsilane and well-known insertion of alkene into the Rh-Si bond accounts for a non-metallacarbene mechanism of a new rhodium-catalyzed silylation of olefins with vinylsilanes.