This study will use magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) to investigate how white and gray matter in the brain changes over time in males with autism. This project involves collaboration between a longitudinal neuroimaging, clinical, and neuropsychological study of late neurodevelopment in autism and the National Alliance for Medical Imaging Computing (NA- MIC). The collaboration will bring brain imaging analysis tools developed by NA-MIC into autism clinical research and form a new multidisciplinary research team. Working together, the computer scientists and clinical researchers will use critical biological questions in autism to "drive" the development of NA-MIC "tools". The critical biological questions are 1) what is the microstructural basis of abnormal brain connectivity during late neurodevelopment in autism, and 2) how is brain microstructure related to deficits, developmental trajectory, and outcome. Understanding the brain-basis of deficits, disease course, and outcome in these individuals is critical for development of autism-specific treatments as well as secondary and tertiary preventive interventions.