This study examined the relations between child internalizing behavior problems and social competence in a sample of young children (N = 166) with autism spectrum disorders (ASD) as they transitioned to early schooling. Previous literature suggested higher rates of comorbid psychopathology in this population of children; however, a limited number of studies have explored the influence of behavior problems and their effect on the social behaviors of children with ASD across time. Further, methodological challenges in the assessment of behavioral and social impairments in students with ASD have increased the utility of multi-informant data when examining these relationships. Results indicated that parents and teachers of children with ASD demonstrate poor agreement on measures of social and behavioral functioning. Additionally, parent and teacher ratings of social functioning collected at the onset of the study were shown to be a significant predictor of children's social skills at the end of their participation (18 months). The study also examined the relation between internalizing behavior problems and ASD symptomatology, and the impact of both of these on the growth of children's social skills. Although results indicated that internalizing behavior problems and ASD symptomatology did not significantly predict social skills growth over time, child behavior problems were shown to predict children's initial status of social skills at the start of the school year. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]