A series of 12- and 18-membered macrocyclic germasilethynes, representatives on a new class of highly unsaturated macrocyclic heterohydrocarbons has been prepared by reactions of bromomagnesium derivatives of diethynyldiethylsilane, bis(ethynyldimethylsilyl)ethyne, and bis(ethynyldimethylsilylethynyl)dimethylsilane with dichloro(dimethyl)- and dichloro(diisopropyl)germanes.