Previous studies have suggested that the glutamate system may be abnormal in the brain of adolescents with autism and that these abnormalities may arise after early childhood. A non-invasive way of measuring glutamate in the brain is by using magnetic resonance spectroscopy (MRS). This technique is based on the same principles as magnetic resonance imaging (MRI), but, instead of images, it provides high frequency spectra that allow the investigators to study the biochemical composition of the brain. In this research, the glutamate concentrations in the brains of adolescents (12-17 years) will be compared between children that are typically developing and those that have autism. The goal of the study is to determine whether adolescents with autism exhibit increased glutamate concentrations.