The reaction O(P-3(J)) + (CH3)(3)SiH --> products (1) has been investigated by the discharge/fast-flow method with mass spectrometric detection (DF-MS) over 298-773 K and by the flash photolysis/resonance fluorescence (FP-RF) technique over 293-549 K. The rate constants from both methods are in close accord and may be summarized by k(1)(T) = 5.6 X 10(-11) exp(-1005 K/T) cm(3) molecule(-1) s(-1) for 290-770 K. There is reasonable agreement with previous room-temperature studies. k(1) is larger than k(2) for O + SiH4 (2), similar to results for triethylsilane and triisopropylsilane [Buchta, Chr.; Stucken, D.-V.; Vollmer, J.-T.; Wagner, H. Gg. Z. Phys. Chem. Neue Folge, to be published], and tri-alkylation is seen to increase the reactivity of the Si-H bonds by similar amounts largely independent of the nature of the alkyl group. This silane activation occurs through lowering the energy barrier to abstraction to form OH + (CH3)(3)Si.. Ab initio analysis of this pathway at the MP2/6-31G*//HF/3-21G(*) level of theory gives relative energies for the transition states of reactions 1 and 2 that agree well with experiment.