Dr. Hazlett's research team at University of North Carolina (UNC) has developed image processing tools specifically designed for highly-efficient, reliable, and valid processing of pediatric magnetic resonance imaging (MRI) data. Their early results from a longitudinal MRI study of brain development demonstrate generalized enlargement of white and gray matter volume in cerebral cortex in autistic individuals at age 2 yrs. This study will track brain development using MRI/DTI (diffusion tensor imaging) scans in 6-10 year olds with autism and controls who have already participated in the longitudinal MRI study of brain development. Forty-two children with autism who have been scanned at ages 2 and 4 will be rescanned at age 6-10. Controls will include typically-developing children and a small subset of children with developmental delay. This study will provide more definitive information about the trajectory of brain growth (regions, tissues, structures, and fiber tracts) as measured on MRI and DTI. Additionally, Dr. Hazlett will be able to explore behavioral features associated with social cognition and ritualistic repetitive behaviors in an in-depth manner now that the children are older (6-10 years old), which may provide important insights into the development of neurobiological mechanisms and behavioral phenotypes in autism.