The overall objective of this project is to improve our understanding of the molecular basis of autism, which will lead to earlier and more accurate diagnosis of Autism Spectrum Disorders (ASD). We hypothesize that ASD is caused by the interplay of genetic and environmental factors, resulting in developmental neurological disability. Subsequent altered neuronal activity can then be profiled by microarray analysis. We believe that there are reproducible differences in gene expression in the peripheral blood of individuals with ASD, compared to controls. Differences in expression patterns will provide a signature for ASD that can possibly be developed into a diagnostic test for the disorder, which does not currently exist. This project has the potential to change the way we classify ASD, as well as provide insight into the functional pathways underlying the condition.