1,1,2,2-Tetramethyl-1,2-disilacycloocta-3,7-diyne I could be prepd. by reaction of 1,8-dibromo-4,4,5,5-tetramethyl-4,5-disilaocta-2,6-diyne with lithium in the presence of catalytic amts. of biphenyl. X-Ray investigations on single crystals of I revealed an almost planar structure adopting C2v symmetry. The transannular distances between the pairs of carbon atoms in the triple bonds are 2.672 and 3.153 .ANG., resp. The anal. of the He(I) photoelectron spectrum of I reveals a strong interaction between the in-plane p-orbitals of the triple bonds and the Si-Si s-bond.