The Wisconsin Twin Panel utilizes the resources of state birth records to study the etiology and developmental course of early emotions, temperament, childhood anxiety and impulsivity, the autism spectrum, and related psychobiological and behavioral phenotypes. The panel currently supports 5 active research studies which involve twins from birth to early adolescence. A range of research methods are employed, including questionnaires and structured interviews with caregivers, home and laboratory-based behavioral batteries, observer ratings, child self-report, psychophysiology, neuroendocrine measures, birth records, genotyping, and cognitive testing. The panel is in the early stages of generating longitudinal findings.