The nucleophilic cleavage of substituted benzyltrimethyl-silanes in DMSO-Hz0 media using tetraalkylammonium fluoride, TAAF, has been studied. The observed rate constants, pseudo first order rate constants, activation, and thermodynamic parameters have been reported. A mechanism for such cleavage has been proposed. The results fit well Hammett equation. The reaction constant, p! value of (6.7) has been reported. The p value is consistent with a substantial negative charge developing in the transition state.