Rats with bilateral, subtotal lesions of the superficial layers of perirhinal cortex were tested in a reaction-to-novelty procedure and in the Morris water maze. Lesioned rats spent significantly more time than did control animals in exploring objects in the reaction-to-novelty test apparatus. In addition, lesioned rats exhibited increased rearing, both in the exploration procedure and in an open field test. Locomotor and grooming activity in lesioned rats was not significantly different from that of control animals. These results suggest that, in the rat, the perirhinal cortex may be involved in the modulation of exploratory behavior, possibly via links with the amygdala. Lesioned rats were not impaired in the Morris water maze; rather, their latencies to find the hidden platform were significantly lower than those of control animals during initial place navigation testing. The latter finding contrasts with the results of our previous work, which demonstrates that more extensive lesions of perirhinal cortex produce water maze deficits.