The results demonstrated that there were significant differences in the effect sizes of studies conducted in the United States versus those conducted in other countries and that studies that were based on samples smaller than 100 children had larger effect sizes. Sample size was also the strongest predictor of the variation in the effect sizes. Additional evidence indicated that early family/parent training was also effective in reducing delinquency and crime in later adolescence and adulthood. The overall findings lend support for the continued use of early family/parent training to prevent behavior problems. Recommendations are made for future research to test the main theories of early family/parent training and detail more explicitly the causal mechanisms by which early family/parent training reduces delinquency and crime. Based on evidence that early antisocial behavior is a key risk factor for delinquency and crime throughout the life course, early family/parent training has been advanced as an important intervention/prevention effort. The prevention of behavior problems is one of the many objectives of early family/parent training, which was the main focus of this analysis. This analysis provides a comprehensive assessment on the evaluation of early family/parent training programs implemented in early childhood in preventing child behavior problems. Tables, figures, appendix, and references