Acid strength and catalytic activity were detd. in com. NaX (1.2), NaY (2.4), mordenite (5.4), or ZSM-5 (Si/Al = 110) zeolite supported Ni-Mo catalysts (4.06-4.57% NiO, 6.37-8.71% MoO3) prepd. by incipient wetness impregnation with aq. Ni(NO3)(2) and (NH4)(6)Mo7O24 solns.at 90 and 110 degrees C and 18-hr. calcination in air at 450 degrees C. The total (Bronsted and Lewis) acidity assessed via n-butylamine chemisorptions run at 150 and 250 degrees C was max. (3.4 mmol/g) and min. (0.8 mmols/g catalyst) in the Y- and the mordenite-supported catalysts. In hydrocracking (300 degrees C, I atm) of n-heptane, the activities (% propene formed in 4 hrs.) followed the order: ZSM-5 (97.8) > Y (96.4) > mordenite (95.8) > X (93.30%). The Ni-Mo/ZSM-5 had mostly (91%) strong acidic centers. The absence of multibranched products suggests n-heptane isomerization and hydrocracking to have run inside the channels of the zeolites.