Whether and to what extent kindergarten children's executive functions (EF) constitute promising targets of early intervention is currently unclear. This study examined whether kindergarten children's EF predicted their second-grade academic achievement and behavior. This was done using (a) a longitudinal and nationally representative sample (N = 8,920, M[subscript age] = 97.6 months), (b) multiple measures of EF, academic achievement, and behavior, and (c) extensive statistical control including for domain-specific and domain-general lagged dependent variables. All three measures of EF--working memory, cognitive flexibility, and inhibitory control--positively and significantly predicted reading, mathematics, and science achievement. In addition, inhibitory control negatively predicted both externalizing and internalizing problem behaviors. Children's EF constitute promising targets of experimentally evaluated interventions for increasing academic and behavioral functioning. [This is the online version of an article published in "Child Development."]