The diagnosis of autistic spectrum disorder (ASD) is subjective because of the complex spectrum of symptoms and the lack of empirical markers. This is due to the fact that little is known about the basic mechanisms underlying the etiology and progression of the condition. However, there is widespread agreement that early diagnosis and appropriate intervention can lead to a better outcome for the affected individual and their families. This study will attempt to identify a serum-based panel of biomarkers for minimally-invasive early diagnosis of ASD and potentially for distinguishing the various subtypes of the condition using state-of-the-art proteomic platforms. The investigators have already identified a prototype panel using the Multi-Analyte Profiling (xMAP®) platform which can distinguish Asperger's subjects from matched controls in a small clinical cohort. They propose to develop this panel further through profiling analyses of additional cohorts reflecting the spectrum of the condition compared to age and gender matched controls. The second phase of the project will test the prototype panel using larger clinical cohorts to identify the most robust biomarker patterns for identification of ASD subtypes at the earliest possible clinical phase. The resulting panels will be deployed using the xMAP® format for maximum utility and ease of use in the clinical setting. The availability of biomarker panels for ASD promises to lead to: 1) increased understanding of the underlying molecular mechanisms, 2) earlier diagnosis of affected individuals, 3) positioning of subjects for early intervention approaches and 4) identification of potentially novel treatment strategies.