Multiple measures of children's emotionality (emotional intensity and negative affectivity), regulation (including attentional and behavioral regulation and coping), and social functioning (teachers' reports of nonaggressive/socially appropriate behavior and prosocial/socially competent behavior; and parents' reports of problem behavior) were obtained for 6-8-year-olds. In addition, emotionality, attentional regulation, and coping were assessed 2 years previously. Social functioning was expected to be predicted by low negative emotionality and high levels of regulation. In general, the data supported the predictions, although the findings for parent reports of problem behavior were primarily for boys. Prediction of social functioning from measures of regulation and emotionality occurred primarily within a given context (school vs. home) rather than across contexts, even though there were relations across reporters within the school or home context. In addition, vagal tone, a marker of physiological regulation, was positively related to competent social functioning and emotionality/regulation for boys, but inversely related for girls.