Neurodevelopmental outcome of children with congenital heart disease includes a wide spectrum of developmental disorders from language and learning disabilities to mental retardation, delayed development, and cerebral palsy. Numerous studies of cardiopulmonary bypass show that this procedure alone does not affect IQ, but length of circulatory arrest and pH management are associated with decreased IQ. Described here is a behavioral phenotype of children with cardiac disease with a low normal IQ and perceptual-motor delays who are temperamentally more difficult. Further investigation of the vulnerability of specific cardiac lesions, mode of treatment, and the behavioral phenotype of children with congenital heart disease along with the influences of family functioning, socioeconomic status, and chronic medical care is warranted.