The effect of oxidation (623 K) followed by low-temperature reduction (433 K) (O/LTR) on a very highly dispersed 1% Ru/Al2O3 catalyst previously reduced at high temperature (753 K) (HTR1) on the hydrogenolysis of ethane (H-2:C2H6 = 10:1) is to increase the turnover frequency (TOF) at 433 K by a factor of about 200 with respect to that shown after HTR1. Its effect on the hydrogenolysis of 2,2,3,3-tetramethylbutane is also to increase TOF, but in addition the demethylation (alpha gamma) mode of reaction is suppressed and the extent of deep hydrogenolysis is increased. EXAFS measurements show that the O/LTR procedure causes first migration and coalescence of oxidic species and then formation of aggregates of larger metal particles; these are, however, amorphous to X-rays. The enhancement of TOF is therefore not explicable by an increase in the active area; it is, however, partially or completely negated by a second high-temperature reduction (HTR2). Similar effects are observed with Ru powder, Mathematical modeling of the dependence of the rate of ethane hydrogenolysis on H-2 pressure by a rate expression predicated on the formation of a partially dehydrogenated intermediate indicates that the rate enhancement given by the O/LTR treatment is chiefly due to an increase in the equilibrium constant defining the dehydrogenation; its value and that of K-H, which defines the H-2 chemisorption equilibrium, are both lowered by HTR2. Possible explanations in terms either of surface morphology or of alterations in electronic character are considered.