This study sought to contribute to the identification of effective interventions in the area of male adolescent aggressive behavior. Existing research includes both group- and single-case studies implementing treatments which typically include an anger-management component and its attendant relaxation and stress-reduction techniques. The design of this study was single-subject with multiple baselines across 6 subjects on 2 behavioral measures. The setting was a residential juvenile justice program for male adolescents, and the treatment was a relaxation breathing exercise. The results of the study were mixed, with improvement on both behavioral measures in 2 of the 6 participants. (Contains 2 figures.)