Studies of ASD over the past 40 years have reported progressively higher prevalence estimates, ranging 0.07-1.8%, and an even higher rate of 2.64% from the most comprehensive, total population-based survey to date. Proposed revisions for the DSM-5 ASD diagnostic criteria, planned for release in 2013, place all ASDs in a single diagnostic category. Differences between DSM-IV and DSM-5 criteria have led to debates over whether the proposed changes will affect ASD prevalence, the way children will be diagnosed with ASD, and possibly even eligibility of individuals for clinical and other services. This is creating confusion and controversy for scientists and parents, which has been exacerbated by the lack of rigorous scientific data. Such challenges can be best addressed by comparing DSM-IV and DSM-5- based ASD prevalence estimates, and determining which individuals, if any, will no longer meet ASD diagnostic criteria, based on DSM-5 criteria. This study uses a total population approach to include both clinical and non-clinical ASD populations, and systematic standardized screening and diagnostic assessment. Specifically, the investigators will utilize the sample from their recently completed and published Korean ASD prevalence study in a cost and time efficient epidemiological approach to comparing DSM-IV and DSM-5 diagnoses.