This meta-analytic review examines 77 published evaluations of parent training programs (PTPs) aimed at improving parenting behaviors and children's externalizing behaviors. The study used meta-analytic techniques to identify program components consistently associated with larger effect sizes. Key components linked to larger effects included increasing positive parent-child interactions, teaching emotional communication skills, using time-out, and requiring skill practice during sessions. Components linked to smaller effects included teaching problem-solving, promoting children's cognitive or social skills, and providing additional services. The findings suggest that certain program components are more effective than others, with implications for program design and selection. Early childhood behavior problems, such as aggression and inattention, predict adolescent and adult deviance. Parent training programs have evolved from focusing solely on changing children's behaviors to addressing parenting practices. These programs now aim to improve children's cognitive, emotional, and physical health, as well as reduce child maltreatment risks. Numerous meta-analyses have explored PTPs, but few have examined specific program components. This study fills that gap by identifying components that reliably contribute to program effectiveness. The study found that components like positive parent-child interactions and skill practice during sessions are more effective. Conversely, components like problem-solving instruction and additional services are less effective. The results suggest that programs can be improved by integrating effective components and eliminating less effective ones, reducing costs and training needs. The study highlights the importance of examining individual program components rather than entire programs or theoretical approaches. This approach provides a richer understanding of what makes PTPs effective, guiding future program development and implementation.This meta-analytic review examines 77 published evaluations of parent training programs (PTPs) aimed at improving parenting behaviors and children's externalizing behaviors. The study used meta-analytic techniques to identify program components consistently associated with larger effect sizes. Key components linked to larger effects included increasing positive parent-child interactions, teaching emotional communication skills, using time-out, and requiring skill practice during sessions. Components linked to smaller effects included teaching problem-solving, promoting children's cognitive or social skills, and providing additional services. The findings suggest that certain program components are more effective than others, with implications for program design and selection. Early childhood behavior problems, such as aggression and inattention, predict adolescent and adult deviance. Parent training programs have evolved from focusing solely on changing children's behaviors to addressing parenting practices. These programs now aim to improve children's cognitive, emotional, and physical health, as well as reduce child maltreatment risks. Numerous meta-analyses have explored PTPs, but few have examined specific program components. This study fills that gap by identifying components that reliably contribute to program effectiveness. The study found that components like positive parent-child interactions and skill practice during sessions are more effective. Conversely, components like problem-solving instruction and additional services are less effective. The results suggest that programs can be improved by integrating effective components and eliminating less effective ones, reducing costs and training needs. The study highlights the importance of examining individual program components rather than entire programs or theoretical approaches. This approach provides a richer understanding of what makes PTPs effective, guiding future program development and implementation.