In the last decade, there has been a dramatic increase in autistic disorders, including pervasive developmental disorder-not otherwise specified (PDD-NOS). There are currently two main therapeutic approaches: Applied Behavioral Analysis (ABA) and the Developmental, Individual-Differences, Relationship-based Model (DIR). Relatively little literature exists on the use of DIR with children beyond preschool. This thesis presents a case study of a nine-year-old boy with PDD-NOS. Observations from individual sessions illustrate ways the DIR model serves as an effective intervention in middle childhood. The DIR model focuses on engagement, back and forth communication, and regulation, which are all essential to a child's development at all ages. In the analysis of the therapy sessions, four areas of development are examined: symbolic play, sensory processing, language and peer interactions. The child's progress in these four areas is documented and the methods and benefits of the DIR approached discussed.