A weight-drop model of spinal cord injury was used to characterize the sensory changes that occur following mechanical trauma to the spinal cord and to determine the relationship of these changes to the extent of lesion. Weight-drop from different heights resulted in significant differences in motor dysfunction between experimental groups. These groups also demonstrated significant differences in the incidence of allodynia (decreased vocalization threshold to mechanical pressure). The incidence of allodynia was higher in the group that had incomplete spinal cord lesions confined to the central and dorsal regions of the spinal cord and lower in the groups that had either more extensive spinal cord damage or no apparent damage.