Seventy-two subjects meeting for both research and DSM IED criteria will be randomly assigned to either 12 weeks of individual CBT, 12 weeks of group CBT or 12 weeks of a wait-list control condition. Subjects will be assessed before and after therapy/wait-list as well as at 3 month and 6 month follow-up. Primary outcome measures will assess aggressive behavior, anger, and the presence of an IED diagnosis at post-treatment, 6-month follow-up and 12-month follow-up. Social and emotional information processing will be evaluated as potential mechanism of change. Trait aggression will be assessed as a potential moderating variable.