This study examined the response of a young child with autism to two play-based intervention conditions: adult-mediated and peer-mediated. The client was five years old, demonstrated moderate-to-severe autism, and exhibited developmental functioning between the 14 to 34 month level. The peer-mediated condition, based on a modified Integrated Play Group approach, utilized a typically developing peer who was three years of age. The study utilized an ABAB alternating treatment design to compare the impact of the adult- and peer-mediated interventions. Results from the current study suggest that the adult-mediated intervention resulted in increased engagement and more sophisticated social-communicative behaviors than the peer-mediated approach for the child with autism. Clinical implications, limitations, and future research directions are discussed
