After multiple, bilateral, cervicothoracic dorsal rhizotomy from C5-T2, rats begin to chew certain areas of the denervated forelimbs. This abnormal chewing behavior is seen in both limbs within 1 mo after deafferentation. It persists for as long as the animals survive. Unilateral sciatic nerve section also leads to chewing of a part of the denervated region, but it does not occur in all cases, the area affected is small and the abnormal behavior eventually stops. The simplest explanation for this phenomenon is that the abnormal chewing behavior derives from the limbs being rendered anesthetic and analgesic. Alternatively, central changes produced by deafferentation may underlie the abnormal behavior. To answer this question, rats underwent simultaneous multiple bilateral rhizotomy and one of several unilateral spinal cord lesions. A unilateral spinal cord hemisection or lesion of the lateral funiculus at C4 prevents chewing of the limb ipsilateral to the lesion. A unilateral section of the dorsal quadrant, the dorsal part of the lateral funiculus, or the tract of Lissauer produces a delay in the appearance of chewing of the ipsilateral limb. The chewing of the contralateral limb is unaffected by these lesions. These results demonstrate that anesthesia and analgesia of the limbs is not the only explanation for the abnormal behavior and suggests that section of the middle and ventral parts of the lateral funiculus is critical for its prevention. It is hypothesized that the chewing behavior is a manifestation of changes in the central nervous system produced by deafferentation which lead to some form of dysesthesia being experienced in the denervated region.