There has been a substantial increase in social interventions for young children with autism. Many of these are based on a developmental or naturalistic behavioral treatment philosophy and use techniques associated with caregiver responsiveness. These interventions can improve social interaction and promote long term development of other social-communication skills. Despite a growing interest in social intervention for older individuals with autism, current interventions are aimed almost exclusively at high-functioning individuals. There are extremely few social interventions available for adolescents and adults with low-functioning autism (IQ less than 50). Reciprocal Imitation Training (RIT) is a naturalistic behavioral intervention for young children with autism that promotes social imitation and engagement. This project examines whether RIT can be effectively adapted to promote social functioning in adolescents with low-functioning autism. The first aim is to modify RIT so that it is appropriate for use with adolescents. Staff members will be administered a questionnaire on the social validity of RIT. This information will be used to make appropriate modifications to the intervention protocol to ensure the developmental appropriateness of the intervention for the adolescents (e.g., use of more age-appropriate materials, implementation during more age-appropriate activities) and to assist in the delivery of the intervention in a residential setting. The second aim is to conduct a pilot randomized clinical trial (RCT) (n=24) of RIT with youths with autism with significant intellectual disability (ID). Participants will be 13- to 21-year-old students at a residential center for individuals with developmental disabilities. Participants in the treatment group (N=12) will receive RIT for 6 months. Participants in the control group (N=12) will receive an equivalent number of hours of individualized instruction. Treatment outcome will be based on standardized and observational assessments of imitation, social engagement, and disruptive behavior at pretreatment, post treatment, and 6-month follow-up. Principal products of this pilot study will be the RIT-A manual, staff training and RCT protocol, and data on recruitment success, intervention fidelity, treatment acceptability; assessment battery feasibility; protocol fidelity, and expected attrition rates and effect sizes. Information obtained from this pilot treatment study will be used to seek support for implementation a larger randomized clinical trial.