The autonomic nervous system (ANS) is responsible for multiple physiological responses, and dysfunction of this system is often hypothesized as contributing to cognitive, affective, and behavioral responses in children. Research suggests that examination of ANS activity may provide insight into behavioral dysregulation in children with autism spectrum disorders (ASD), however, there is wide variability in samples, methods, and measures reported. The purpose of this review is to describe frequently reported cardiac ANS measures; discuss theoretical models linking ANS measures with neurological structures; and synthesize pediatric literature using ANS measures on typical and ASD samples. Such a synthesis will provide researchers with a foundation for the use of ANS cardiac methods and measures in ASD research.