Using retrieving and other tests, the maternal behavior of a series of albino rats was tested before and after operative procedures. All lesions were made electrolytically and were stereotaxically placed. Motor acts observed during the behavioral tests included retrieving pups, licking pups, adopting the nursing position over retrieved pups and nest forming activities. Results of the operative procedures indicate that sham operations and ablations of a narrow strip of neocortical tissue lateral to the cingulate cortex do not appreciably alter the normal behavior pattern or interfere with the adequacy of maternal care. Animals with lesions of the anterior and posterior cingulate cortex (resulting in retrograde degeneration in the anterior thalamic nuclei) showed a disruption of these motor patterns including a distinct qualitative change in behavior towards pups. Slow retrieving with frequent pauses for grooming or sniffing about the cage, licking of unretrieved pups and little inclination to nurse pups characterized the behavior of these animals during the retrieving tests. All motor patterns seen in the normal animal were expressed by these rats but often in an irregular and confused manner. Pups would be repeatedly brought into and carried out of the nest site or dropped randomly about the cage. The nursing position would be adopted over one or two pups, in or out of the nest site, while the other pups were ignored. Judging from the relatively short latency of responding to the pups and nesting material and by the excitement evident in their aberrant pup retrieving and nest forming behavior, there seemed to be little or no loss of maternal motivation. The pups and nesting material were adequate stimuli to initiate the various motor acts observed in control animals. This aberrant behavior improved over repeated tests and by the third or fourth postpartum day the confusion seen in the earlier tests was less evident and most behavioral scores were close to the normal range. However, when these animals were tested in a strange, brightly illuminated cage, a thorough disruption of maternal behavior again occurred. Pre- and postpartum injections of prolactin resulted in no improvement. Supplying the animal with a small box with a narrow opening (a nest site preferred by normal animals) was also without effect in reducing the disturbed maternal behavior pattern. Lesions limited to the anterior or posterior cingulate cortex resulted in an intermediate loss which quickly improved during subsequent testing. Loss in maternal behavior in animals with partial and full cingulate lesions were significantly correlated with the severity of retrograde degeneration in the anterior thalamic nuclei. Maternal behavior (pup retrieving) which was induced in castrated male rats by exposing them to 1-3 day old pups each day did not suffer from neocortical lesions, but was disrupted by cingulate cortical lesions. It was concluded that the cingulate cortex in the rat participates in the integration or organization of complex unlearned activities.