Autism spectrum disorders (ASD) have known heritable and more recently recognized environmental contributions. Identifying environmental factors involved in ASD etiology is thus a priority for researchers as well as for Autism Speaks. Progress towards this goal depends on collecting data on environmental factors that may have influenced the development and course of ASD during critical time windows. The objective of this research project is to address the Autism Speaks’ targeted priority of discovering and characterizing risk factors for ASD, by developing, refining, validating, and feasibility testing a data-collection tool designed to assess medical and environmental exposures potentially relevant to ASD. Because epidemiologic, neuroanatomic, and animal studies support the prenatal and early life origins of ASD, this self-administered questionnaire asks parents to report exposures during peri-conceptional, pregnancy, and postnatal periods. This tool will cover broad exposures potentially linked to neurodevelopment and ASD, including medical history and procedures, maternal lifestyle and nutrition, exogenous chemicals and toxic compounds. The specific aims are: Phase 1: To select, validate, and refine medical and environmental exposure questions drawn from multiple studies for inclusion in a pilot instrument; Phase 2: To validate the instrument on a sample of 150 participants in the MARBLES (Markers of Autism Risk in Babies – Learning Early Signs) prospective cohort of women and their at-risk pregnancies; and Phase 3: To assess the feasibility of this instrument by enrolling 200 families each from the CHARGE and AGRE studies and requesting that they complete it and provide feedback on the experience. There are currently no validated instruments for environmental exposure assessment during gestation or infancy that would be appropriate for widespread implementation in typical ASD studies. Access to a new, low-burden instrument will help make evaluation of environmental exposures more standardized and feasible for a variety of ongoing and new studies of ASD and other developmental outcomes. This will not only allow more widespread environmental data collection relevant to ASD, but will assist in combining environmental data across studies to more powerfully examine rare exposures, exposures with relatively weak effects, and interaction effects.