The condensation reactions of secondary deuteriosilanes to give oligomer products in the presence of the catalyst precursor Cp2MCl2/nBuLi have been investigated. The products from PhMeSiD2 with M = Zr are not the expected deuterium-terminated chains D(PhMeSi)xD but a mixture of isotopomers with an average deuterium content near two per oligomer, as determined by mass spectroscopy and with deuterium located at silicon as well as the methyl groups, as shown by 2H NMR of isolated oligomers. Deuterium scrambling in the oligomers was not observed in the condensation of PhEtSiD2 with all three catalyst systems and only marginally in the products produced from the condensation of PhCH2(Me)SiD2 (M = Zr). The cocondensation of PhMeSiD2 and TolMeSiH2 provides a near-statistical distribution of combinations of disilanes through tetrasilanes with deuterium scattered almost equally within each combination including those that contain only TolMeSi units. The monosilane product PhMeBuSiD which is believed to form from hydrosilylation of coordinated butene in [Cp2Zr-(butene)] contains from three to eight deuteriums with an average between four and five. Mechanisms for enhanced deuterium incorporation in PhMeBuSiD and deuterium scrambling in the oligomers produced from PhMeSiD2 are proposed that have features in common.