Decreasing the ring size of a cyclic allene to rings of fewer than 10 carbons results in deviation of both the normal C=C=C linearity and the orthogonality of the dihedral angle.' To date, the smallest isolable cycloallene is 1-tert-butyl-1,2-cyclooctadiene,2 and the smallest for which structural information is available is the phenylurethane derivative of cyclonona-2,3-dien-1-oJ,l which is bent to 168° and twisted to a dihedral angle of 79.8°. Encouraged by our recent success in the synthesis and structure determination of a tetrasilacyclohexyne,4 we have pursued the syntheses of strained silacycloallenes and report herein the first examples of isolable 6- and ?-membered rings containing 1,2-diene units.