Sibling, twin and family studies have shown that genetic changes play a major role in ASD. The estimated rates of chromosome abnormalities in persons with ASD range from 5-48%, depending on whether subjects have cognitive delay and/or physical anomalies. Small chromosomal anomalies, such as microdeletions and microduplications, might be relatively common and clinically important markers for identifying underlying genetic causes, including genes conferring susceptibility to ASD. This study will undertake DNA-based candidate gene studies with genomic microarray screening for autism-related microdeletions and microduplications in at least 200 cases from different affected families. In addition, rigorous clinical phenotyping and 3-dimensional craniofacial analysis will be performed in these individuals. This project aims to identify unique autism subgroups based on standardized behavioral and craniofacial analysis and link them to specific genetic markers. Significance: This project has the potential to improve ascertainment and diagnosis, as well as a better understanding of the relationship between genetic abnormalities and physical and behavioral attributes in ASD.