Investigated the partial reinforcement of conditioned suppression in 28 male albino Holtzman rats with an independent groups design. Ss at shock reinforcement schedules of 30, 50, 70, 90, and 100% developed conditioned suppression, and did not differ from each other. A 10% group did not condition and did not respond differently from a 0% control group. For the 30% and greater Ss responding prior to, during, and following CS presentations were all significantly lower than responding for the 0 and 10% Ss in those intervals (p < .01 for all comparisons). Results replicated similar studies but were dissimilar to comparable human eyelid studies and some infrahuman studies of heart rate or salivation by dogs. They were also dissimilar to a conditioned suppression study which manipulated shock reinforcement schedule within Ss. (18 ref.) (PsycINFO Database Record (c) 2006 APA, all rights reserved)