Preventing problem behavior requires an understanding of earlier factors that are amenable to intervention. The main goals of our prospective longitudinal study were to trace trajectories of child externalizing behavior between ages 3 and 10 years, and to identify patterns of developmentally significant child and parenting risk factors that differentiated pathways of problem behavior. Participants were 218 3-year-old boys and girls who were reassessed following the transition to kindergarten (age 5-6 years) and during the late school-age years (age 10). Mothers contributed ratings of children's externalizing behavior at all three time points. Children's self-regulation abilities and theory of mind were assessed during a laboratory visit, and parenting risk (frequent corporal punishment and low maternal warmth) was assessed using interview-based and questionnaire measures. Four developmental trajectories of externalizing behavior yielded the best balance of parsimony and fit with our longitudinal data and latent class growth analysis. Most young children followed a pathway marked by relatively low levels of symptoms that continued to decrease across the school-age years. Atypical trajectories marked chronically high, increasing, and decreasing levels of externalizing problems across early and middle childhood. Three-year-old children with low levels of effortful control were far more likely to show the chronic pattern of elevated externalizing problems than changing or low patterns. Early parental corporal punishment and maternal warmth, respectively, differentiated preschoolers who showed increasing and decreasing patterns of problem behavior compared to the majority of children. The fact that children's poor effortful regulation skills predicted chronic early onset problems reinforces the need for early childhood screening and intervention services.