Structure-resonance theory has recently been shown to correlate and to predict various physical and chemical properties of ..pi..-electron hydrocarbons. The major advantage of this theory is its simplicity. Its application requires only an enumeration of Kekule' structures, since it has been shown that an algorithm, logarithm of the Kekule' corrected structure count, gives an excellent approximation of the gound-state eigenvalues of the structure-function Hamiltonian matrix. The purpose of this contribution is to show that the structure-resonance theory can be used to correlate the rates of both the deuterium-hydrogen and hydrogen-deuterium exchange reactions of benzenoid hydrocarbons. Logarithms of the rates of deuterodeprotonation of nine alternant hydrocarbons and protodedeuteration of five hydrocarbons containing 17 and 12 different reaction sites, respectively, are correlated with the logarithms of the structure counts of the intermediate, ln SC/sub I/, and the reactant, ln SC/sub R/, and with their ratio, ln (SC/sub I//SC/sub R/). The quality of the correlations is very good. The results indicate that the differences in reactivities of benzenoid hydrocarbons in aromatic substitution reactions are due to differences in their resonance energies and that hyperconjugation does not play a significant role in the stabilization of the intermediates in the reaction studied.