The reaction of elemental germanium, hydrogen chloride, and ethylene with copper(I) chloride catalyst gave ethyltrichlorogermane with a 66% selectivity, tetrachlorogermane also being formed. The addition of tetrachlorogermane to the reaction system increased the formation rate of ethyltrichlorogermane. The reaction of germanium, tetrachlorogermane, and butadiene resulted in the formation of 1,1-dichlorogermacyclopent-3-ene. These results indicate the intermediacy of dichlorogermylene, which is formed by the reaction of elemental germanium with tetrachlorogermane. In place of ethylene, allyl chloride was fed with hydrogen chloride. Allyltrichlorogermane was obtained with a 92% selectivity together with a small amount of tetrachlorogermane. It is highly plausible that the formation of allyltrichlorogermane is caused by the insertion of dichlorogermylene intermediate to the carbon - chlorine bond of allyl chloride.