This study used data from the National Institute of Child Health and Human Development Study of Early Child Care to examine relations between parenting, self-control, and externalizing behavior among 1st graders. Of special concern was the relation between opportunities for productive activity and behavior problems and whether the relation was mediated by self-control. Evidence in favor of the hypothesis was observed for both mother-reported and teacher-reported externalizing behavior even with substantial controls on the models examined. Self-control also mediated relations for maternal harshness and maternal sensitivity. Somewhat surprisingly, the direct effect of maternal sensitivity on mother-reported externalizing behaviors was positive.