This study was designed to test whether there is a functional relationship between sensory stimulation and stereotyped movements (SM). Four children with autism and intellectual disability (according to DSM-IV criteria) who showed stereotyped movements were studied. The Short Sensory Profile was used to define whether a child perceived stimulation within each sensory modality as aversive, attractive, or neutral. The Stereotyped and Self-Injurious Movements Interview was used to identify each child's repetitive movements. Children were then exposed to sensory stimuli that were neutral, aversive or attractive. Results indicate that children: (a) initiate or increase stereotyped movements immediately following the onset of an aversive stimulus, (b) terminate or decrease stereotyped movements following the onset of an attractive stimulus and (c) initiate or increase stereotyped movements during periods of neutral stimulation. We conclude that stereotyped movements are functionally related to sensory stimulation; individuals who frequently engage in stereotyped movements may do so in order to cope with under-stimulation and aversive over-stimulation.