In 2006, Autism Speaks funded a group of projects to test the efficacy of various instantiations of parent-implemented treatments to toddlers under the age of 25 months who met diagnostic criteria for autism. Given that the majority of these projects intended to use random assignment to experimental and comparison groups, measured child outcomes from children of similar ages, and parent-implemented treatments, there is a good probability that there will be exceptional comparability of the data among studies. This is an ideal situation for meta-analysis, which seeks to estimate the population treatment effect size and identify and estimate the covariates of treatment effect sizes. A meta-analysis across these studies would provide answers to the broader question of the efficacy of parent-mediated interventions compared to community interventions to one year olds with ASD, maximizing the power to answer this via meta-analysis. This is very important to this group of studies, many of which have too few subjects to fully power analyses from individual projects. This project will provide funding to conduct such a meta analysis to be completed in 2012.