This book provides a short overview of the development of aggressive behavior, assessment guidelines and the contents and materials of two training programs. The Training with Aggressive Children and Training with Adolescents are recognized multimodal cognitive-behavioral training programs developed for the treatment of aggressive behavior (oppositional defiant disorder, conduct disorder) in children and adolescents. The individual and group training modules are supported by parent and family counseling. The training programs are based on the modern learning theory. The effectiveness of the training programs was proven through empirical studies. The children and adolescents concerned showed important improvement and significant changes with respect to problem behavior as well as an increased prosocial behavior.