The hydrodenitrogenation (HDN) reactivities of quinoline (Q) and several methyl-substituted quinolines (MQ) were determined over a NiMo/Al2O3 catalyst and a CoMo/Al2O3 catalyst using a fixed-bed reactor at 613 K and 3.1-MPa pressure. Compared to Q, HDN conversions were about the same when methyl groups were on the aromatic ring, but they were substantially lower for methyl groups on the N-ring, except for 2-MQ. The CoMo catalyst was somewhat more active than the NiMo catalyst. All MQs and Q rapidly reached equilibrium between the Q and the 1,2,3,4-tetrahydroquinoline (THQ1) methyl analogs. It was found that total and HDN activities were roughly related to their respective equilibria, except for 2-MQ, in which the methyl group provides a positive influence. The intrinsic rates of hydrogenolysis of the THQ1s to o-propylamines were correlated with the electrostatic potential at the nitrogen atom in the respective THQ1 molecule, most likely related to the adsorptive affinity or reactive affinity on the active site.