Employing typically developing children and adults as models of appropriate behavior for children with autism and other developmental disabilities has been a common practice for more than four decades, and peer modeling serves as one of the theoretical cornerstones of inclusion and related innovations. In addition to examining adult and peer modeling, this study extends previous modeling research by including a subset of peers?siblings. The authors employed a parallel-treatments single-subject design counterbalanced across stimulus sets and replicated across three participants to extend previous research on the effectiveness of peers, siblings, and adults as models for teaching novel language skills to children with autism spectrum disorder. Participants learned the target skills under all three modeling conditions.