This research aims to identify causal factors that determine the developmental course of toddlers who have a “high risk” for autism (ASD). For this purpose we will evaluate the efficacy of an innovative parent education program that targets children's communication skills in the context of parent-child play interactions. The intervention procedures are specifically tailored to the needs of toddlers between 18 and 24 months who show communication delays consistent with autism. Across two research sites (UCLA: Connie Kasari, Hunter College/ CUNY: Michael Siller), eighty parent-child dyads will be recruited and randomly assigned to either the experimental intervention or a control condition. Subjects assigned to the experimental group will participate in 12 home-based intervention sessions. The experimental intervention is manualized, follows an illustrated workbook for parents, and uses individualized video-feedback, modeling, and coaching strategies to help parents establish play interactions that promote communication. All participants take part in comprehensive baseline as well as 6- and 12-month follow up assessments. Families in the control group will also be invited to participate in an oral feedback session to discuss the results from these assessments. Children's involvement in other forms of intervention will be monitored using a validated intervention log so that the moderating effects of these treatments can be examined. Because the intervention proposed in this research focuses on parent-child interactions, one aim is to evaluate whether the quality of these play interactions can be modified. Given the expectation that this can be accomplished, the study will also investigate the extent to which these modifications result in changes in child development as well as parental motivation, cognition, and affect. Based on results from two long-term longitudinal studies of children with autism, we expect that improvements in the quality of parent-child play interactions will lead to improvements in non-verbal communication as well as the ability to understand and use spoken language.