In a sample of 153 children from preschool through second grade, relations between the use of emotion regulation strategy and children's expression of anger and sadness were coded during an observational task in which children were intentionally disappointed in the presence of the mother. Multilevel modeling was used to examine strategy use and current and subsequent expressions of anger and sadness. Results indicate that mothers' use of attention refocusing and joint mother-child cognitive reframing lead to lower intensity of expressed anger and sadness. Younger children expressed more sadness than older children, and maternal attention refocusing was less successful among older children than younger ones. Implications of these results for assessing the socialization of emotion regulation in preschool and school-age children are discussed. (Contains 6 tables.)