Longitudinal support was obtained for a positive relationship between cognitive and social development. From a large sample of kindergarteners, three groups of 12 children of comparable age and IQ were selected as displaying substantial, moderate, or no mastery of Piagetian concrete operations. From kindergarten through second grade, the social development of the initially high cognitive group exceeded that of the initially low cognitive group in the areas of empathy, communication and role taking. Although all groups improved, cognitive differences present in kindergarten persisted through second grade. (Author/JMB)