In 2013, the American Psychiatric Association will release the newest version of the Diagnostic and Statistical Manual for Mental Disorders. The transition from DSM-IV TR to DSM-5 definitions of Autism Spectrum Disorders (ASD) is based on extensive research regarding the symptom presentation of ASD. However, little information is available regarding the impact of the change. The primary goal of this study is to investigate ASD prevalence using two methodologies (record review and population-based screening and assessment) and two ASD case definitions (DSM-IV TR and DSM-5) within the context of the South Carolina Children's Educational Surveillance Study (SUCCESS). SUCCESS is a population-based screening and assessment study funded by Autism Speaks to determine the prevalence of ASD among 8-year-old children in South Carolina (children born in 2004; n=8500). The study has several complimentary goals including: 1) establishing an accurate prevalence estimate for ASD to compare to similar studies from other countries; and 2) comparing the prevalence estimate to that obtained through the CDC Autism and Developmental Disabilities Monitoring (ADDM) Network's record review methodology. The goal of this study is to compare DSM-IV and DSM-5 criteria for ASD in a group of children who have been identified as being at risk for ASD through population-based screening and/or through record review and abstraction. This is among the first studies to be prospectively designed to test the impact of the changes in diagnostic conceptualization of ASD, and to include the newly described Social Communication Disorder. If differences in prevalence are identified, the findings will allow the identification of child-specific factors that might lead to differential identification (e.g., sex, socioeconomic status (SES), cognitive functioning, specific ASD-related behaviors, co-morbidities, degree of impairment and medical history). In addition, this study had the potential to provide important information regarding sources of information in the ASD assessment process, and on the relationship between diagnosis and performance on ASD screening and assessment instruments.