The proposed project will serve as a pilot study to assess feasibility of conducting a full investigation of whether intake of acetaminophen or other analgesics in early childhood is a risk factor for autism/ASD. Both the pilot and, if appropriate, the full study, will take advantage of data that have been generated from The CHARGE (Childhood Autism Risks from Genetics and the Environment) Study, an ongoing NIEHS-funded population based case-control study of children with autism or ASD, children with developmental delay but neither autism nor ASD, and typically developing controls recruited from the general population. For the pilot study, we will focus on a subset of cases of autism or ASD and a similar subset of typically developing controls and their early childhood medical information, including infections, fever, and use of acetaminophen, aspirin, and ibuprofen. Sources of data on intake of these medications and on their indications are primarily the maternal reports and pediatric records. These will be supplemented by product information to capture the wide range of over-the-counter treatments that may contain acetaminophen, aspirin or ibuprofen as an adjunct ingredient. The pilot study will evaluate the feasibility of obtaining a relatively comprehensive picture of exposures. In the full study, prevalence odds ratios will be calculated for each of these exposures in logistic regression models adjusting appropriately for sociodemographic, medical, and other potentially confounding variables.