Following criterion of 90 percent correct responses to a 1,000-Hz tone on a 50 percent reinforcement schedule, 8 of 12 dogs were subjected to lesions of the medial or lateral prefrontal cortex. Three types of auditory frequency generalization tests followed separated by a period of reacquisition of the instrumental response. A sampling procedure of generalization assessment, wherein a block of test trials was contained within 15 partially reinforced trials and repeated over 16 days, revealed complete generalization in the medials and rapid, but discriminative responding in the laterals. The second generalization test was conducted in complete extinction over 5 days. The medials yielded discriminative performance and least overall resistance to extinction, while the laterals showed a higher amount of frequency control and minimal extinction effects. Go-no go differentiation training preceeded the last generalization test [CS(+) = 1,000 Hz; CS(-) = 600 Hz], resulting in retarded acquisition in the laterals and easiest acquisition in the medials. The last generalization test suggested that all groups were comparable, with some trend toward more rapid extinction in the medial dogs. Collectively, the data indicated that performance was determined by the interacting functions between the specific lesions and the density of reinforcement present in the testing procedure.