Autism spectrum disorder (ASD) is often associated with impairments in executive control, the neural activities that allow for and produce goal-directed actions. The present study will use structural and functional brain imaging to more characterize brain activity in autistic adolescents during tasks which involve executive control, and to more fully define how executive control is affected in ASD. Functional magnetic resonance imaging (fMRI) will be used to visualize regional brain activities in 40 high-functioning adolescents with ASD and an age-matched control group during their performance of an executive control task. The resulting data will be used to determine whether the impairments experienced by individuals with ASD are characterized by brain activity typical of a failure to maintain an appropriate overall approach to the task at hand, or a failure of moment-by-moment implementation of executive control. As well, brain regions demonstrating abnormal activation in ASD individuals during executive control tasks will be further examined for atypical structure and connectivity to other parts of the brain. Determining the aspects of executive control and associated brain structures that are affected in ASD will be of use in the design and selection of appropriate behavioral therapies.