The purpose of this study was to examine the collateral relationship between engagement in social interaction with peers and the occurrence of stereotypic behavior for two children with severe disabilities. Peers without disabilities were taught to make social initiations to two children with autism and other severe disabilities who engaged in high rates of stereotypic behavior. When the peers made social initiations and the children with disabilities increased their engagement in social interaction, collateral decreases occurred in their stereotypic behavior. Within an ABAB design, the functional relationship between these variables was demonstrated. Implications of these findings for designing interventions for promoting social integration and their possible effects on stereotypic behavior are noted.DESCRIPTORS: autism, challenging behavior, nonhandicapped peers, social interaction, stereotypic behavior Stereotypic behavior and social isolation are defining characteristics of autism (Dawson, 1989;Schreibman, 1988). Stereotypies are highly visible and unusual behaviors that may take the form of body rocking, mouthing, or complex hand a n d finger movements, although vocal stereotypies also occur for