Abstract The action of the Me 3 SiCl/Mg/HMPT system on various acetylenic hydrocarbons leads by a new route, to mono-, di-or poly-silylated compounds. Most of the derivatives synthetized are new. The persilylation of phenylacetylerie led to a heptasilylated derivative with an unexpected structure, whereas the direct monosilylatmon, which leads to PhC CSiMe 3, can be carried out in satisfactory yields.