Anger resulting in Aggression can be a significant problem for some people with Intellectual Disabilities. Carers were asked to complete a provocation inventory and an attribution scale before and after a group cognitive behavioral intervention aimed for anger and at similar points in time for a waiting list control. When compared using an analysis of variance results suggest that staff perceive a significant reduction in aggressive responses for participants who took part in the intervention. A regression analysis of factors that may influence the amount of change observed suggests that greater change was achieved if participants were accompanied by carers and had been attributed by carers as having an emotional cause for their behavior. (Contains 3 tables.)