Because of the need to identify large numbers of participants for genetics studies and other investigations of the causes of autism spectrum disorders (ASD), researchers require a way to rapidly screen large numbers of children and identify those who are highly likely to have a diagnosis of ASD. This project aims to develop a research screening instrument based on questions from the Social Communication Questionnaire (SCQ) and the Autism Diagnostic Interview- Revised (ADI-R) that can be more effectively and practically employed in research studies of ASD. The newly developed measure will be the ADI Research Screening Questionnaire, a brief parent-report instrument that is designed to identify ASD in children ages 2 to 18 years. Development and validation of the new measure will involve two very large groups of children from multiple sites across the U.S. This project will provide researchers with the ability to quickly select potential participants so that they can more effectively carry out their investigations into the causes of ASD.