This NIH Funding Opportunity Announcement (FOA), supported by funds provided to the NIH under the American Recovery & Reinvestment Act of 2009 (“Recovery Act” or “ARRA”), Public Law 111-5, solicits applications for the following topic areas relevant to research on the heterogeneity of Autism Spectrum Disorders (ASD): Measurement development, Biomarkers/biological signatures, Immune and central nervous systems interactions, Genetics/genomics, Environmental Risk Factors, Model development, Treatment and intervention, and Services research. This FOA provides support for the R01 grant mechanism which supports larger scale studies for which preliminary data exists and proof-of-principle has been established.