Based on empirically derived principles of learning theory, behavior modification requires the careful identification of the problem behaviors and their results, and the setting of goals based on the client's ability to perform the desired behaviors. According to behavioral theory, aggression is a learned response that is maintained by such consequences as attention, recognition, relief from excessive stimulation, and the acquisition of concrete rewards. Treatment requires the systematic use of techniques for requires the systematic use of techniques for accelerating and decelerating behavior as well as improving interaction skills. Both positive and negative reinforcements are used; however, punishment is not used alone. Instead, withdrawal of positive reinforcement through the time-out procedure can be used effectively in conjunction with positive reinforcement procedures. Time-out is complicated in practice, but is a mild punishment that does not bring about undesirable psychological effects. Extinction involves ignoring annoying behaviors. It has limited usefulness with aggressive adolescents because of the dangers of ignoring early reaction signs. Self-control approaches to behavior modification teach clients to identify and manipulate their own controlling variables. The consensus of the literature is that a combination of behavioral approaches is needed to treat the aggressive teenager. These procedures are most useful in a residential setting where maximal control exists over the environment. However, data are equivocal regarding generalization and duration of treatment effects, suggesting that the usefulness of behavioral approaches with aggressive adolescents lies in institutional control. Attention is needed on how to increase the chances of generalization for specific cases. One hundred references are listed.