Hydrocracking of a mixture of naphthalene and phenanthrene in the temperature interval 300-370°C offered information on the temperature dependence of rate, equilibrium and adsorption constants. The number of parameters needed to describe phenanthrene and naphthalene hydrocracking kinetics was then reduced by the development of temperature-independent quantitative structure/reactivity relationships (QSRRs) for the activation and reaction enthalpies and entropies. Activation energies for isomerization and ring opening reactions were correlated with the heat of formation of the intermediate carbocation. Activation energies for hydrogenation were correlated with the standard reaction enthalpy. The principle of compensation was successfully used to relate entropic quantities to enthalpic quantities. The existence of QSRRs allowed the kinetics of naphthalene and phenanthrene hydrocracking to be represented very satisfactorily, over a wide temperature range, in terms of just 17 QSRR parameters. These 17 parameters summarized the chemical information in 576 rate, equilibrium, and adsorption constants. Thus, the QSRR approach reduced the number of modeling parameters by about 97%.