In order to formulate a hypothesis regarding the etiology of toe walking, the sensory processing abilities of 17 mentally retarded children who toe walk were examined. A galvanic skin response was used to compare reactions of the mentally retarded children and a group of normal children to a variety of sensory stimuli. Galvanic skin response testing did not reveal significant differences between the two groups in processing sensory input. Scores of the mentally retarded children from a postrotary nystagmus test were compared to values for normal children of the same age, and the results indicated that vestibular dysfunction was present in all of the subjects. We hypothesize that children may toe walk to increase somatosensory input to the lateral vestibular nucleus (Deiter's) and the lateral vestibulospinal tract to facilitate support tone in the lower extremities during walking.