PREVIOUS reports in the literature have suggested that children with significant congenital heart defects, especially of the cyanotic types, may have delayed motor development and a higher than expected incidence of mental subnormality.1-3Two of the factors that have been considered to affect the mental development of these children have been the hemodynamic severity of the lesion and environmental deprivation due to physical incapacity.1-3 This study was designed not only to assess the roles of the hemodynamic abnormality of the defect and environment, but also to evaluate other factors that may make a crucial contribution to the mental status of these children. In this study of children with congenital heart disease, the hypothesis that there is an association among small head circumference, mental subnormality, and growth failure was tested.4The study also evaluated the reliability of using motor-development milestones to predict ultimate mental development in children with