The purpose of this Funding Opportunity Announcement (FOA) is to encourage research grant applications to support research designed to elucidate the etiology, epidemiology, diagnosis, and optimal means of service delivery in relation to Autism Spectrum Disorders (ASD). An R03 grant supports small, discrete, well-defined projects that can be completed in two years and that require limited resources. R03 applications may include development of new research methodologies or technology, secondary analysis of existing data, and pilot or feasibility studies. Preliminary data are not required, particularly in applications proposing pilot or feasibility studies. Applicants pursuing exploratory/developmental research to support early and conceptual stages of project development should consider the companion R21 FOA, PA-21-200. Applicants pursuing larger studies in established scientific areas where preliminary data are expected should consider the companion R01 FOA, PA-21-201.