This is a supplement to a previously awarded grant with the same title. Despite a strong influence of genetics, environmental factors are likely to play a causal role for many children with ASD. The proposed project will continue an epidemiologic study of the environmental and genetic causes of autism that was initiated under the University of California-Davis Center for Children's Environmental Health (CCEH). This project, known as the CHARGE (Childhood Autism Risks from Genetics and Environment) Study, is a comprehensive, population-based case-control investigation of underlying causes for autism and triggers of regression. Cases are children with autism and two other groups are included: children with developmental delay and children selected at random from the general population. The proposed study will address the possible role of exposures during the preconceptional, gestational, prenatal, and early childhood periods. Environmental exposures to be studied include infections, assisted reproductive technology, medications, pesticides, brominated flame retardants, and metals. Researchers will also evaluate these environmental factors in conjunction with genes involved in xenobiotic metabolism or identified by gene expression pattern results.