A comparative analysis of selected examples of compensation behaviour, reported in the literature or identified here in published rate studies for heterogeneous catalytic reactions, showed that the isokinetic temperature often occurs within the interval of the kinetic measurements. (At the isokinetic temperature the rate constants for all reactions of the set are equal). Detailed comparisons of data for a diverse group of nickel metal catalyzed cracking-type processes showed significant variations of the magnitudes of the activation energies reported for ethane hydrogenolysis, though levels of reactivity were similar to other chemical changes in the set. It is also concluded that the factors determining the magnitude of Arrhenius parameters for many surface processes are insufficiently well understood to warrant the formulation of detailed mechanisms of the contributory surface reactions. It is also concluded here that the similarity of reactivities over a range of reaction temperatures, for a set of rate processes, is demonstrated by the existence of compensation behaviour. This observation may be useful in providing insights into the identity of common factors controlling reactivities within each group of isokinetically related reactions. A similar level of reactivity characterizes the compensation set. A theoretical explanation of the magnitudes of Arrhenius parameters for many surface processes is not at present practicable because we have insufficient knowledge of the conditions and controls prevailing. Mechanistic proposals are often based on presumed extensions of the theory accepted for homogeneous rate processes.