Rats lacking gustatory neocortex and normal rats were familiarized to either HCl (10-1.6 M) or quinine HCl (10-4 M) solutions during free-drinking trials. They were trained subsequently to avoid either the familiar or the novel taste stimulus, using a balanced design, by pairing the to-be-associated taste with i.p. injections of apomorphine HCl. Balanced, nonpaired presentations of the other taste solution and water were presented also. Normal rats more efficiently learned to avoid the novel compared with the familiar taste. Rats with gustatory neocortex lesions did not differentiate novel from familiar tastes. They learned aversions to both in a manner highly similar to the aversion learning of familiar tastes by the normal group. Rats lacking gustatory neocortex displayed an associative deficiency, relative to normal, only when they were trained on novel stimuli. This observation supported an earlier suggestion that gustatory neocortex lesions disrupt the conditionability of taste stimuli by reducing or eliminating responses to taste novelty. This suggestion was supported further by the absence of a neophobic response in the operated rats to the 1st presentation of a taste stimulus.