Preschoolers' expression of various emotions and overall social-emotional competency may be related to mothers' emotional responsivemness to children's emotions. This research investigated, through extended naturalistic observation, (1) how maternal emotion displays differ according to antecedent child emotion (happy, sad, angry, or afraid) and (2) the prediction of particular emotions expressed by the child and of ratings of the child's social-emotional competence (when the mother was absent) by prevalence of maternal emotions, maternal responses to the child's emotion, and maternal psychosocial functioning. Subjects were 29 mother-toddler pairs. Multiple regression analyses showed that an aggregate of maternal emotional dialogue components, maternal current functioning, and/or prevalent maternal emotions were efficient predictors, in combination, of children's various emotions and of children's social-emotional competence. Implications regarding the mother-child affective environment, socialization of emotion and social competency, and developmental methodology are discussed. (Author/DST)