Relative to baseline scores that did not differ significantly between the experimental and control groups, the experimental group scored higher on perceived self-efficacy compared to the control group at the followup assessment. In addition, the experimental group showed less perceived stress and more adaptive coping after program completion and at the followup assessment. Age-dependent intervention effects indicated that early adolescents primarily benefited from the treatment. Although these effects must be replicated using a randomized design, the findings from the current assessment indicate that the program strengthens important protective factors for the psychosocial development of adolescents. The school-based Anti-Stress-Training (AST), with elements of experiential education, consisted of 6-week training for students, coaching sessions for teachers, and information sessions for parents. Seventeen teachers were trained to deliver the AST to their students during class. The program applies cognitive-behavioral techniques such as cognitive restructuring, self-control techniques, problem solving, modeling, role play, prevention of relapse, and transfer into daily life. The model assumes that cognitive restructuring and the acquisition of emotion focused coping skills should enable students to reduce psychological stress. In the evaluation process, adolescents evaluated the application of the booklet, the usefulness of the booklet, whether they applied the booklet's advice in daily life, and training acceptance. Perceived stress was assessed with seven items. Coping was measured with the German Coping Questionnaire for children and adolescents. Based on a questionnaire developed by Jerusalem and Mittag (1995), students' general, academic, and social self-efficacy was measured with eight items. 6 tables, 3 figures, and 61 references