The effects of a 3-day training course in the management of aggressive behavior in services for people with autism spectrum disorders were investigated using a quasi-experimental design. An experimental group received training over a 10-month period and a contrast group, which had received training before this study, did not. Staff training increased carer confidence, but there were no training effects of measures of staff coping, support or perceived control of challenging behaviors. Staff reports of service user challenging behavior management difficulties decreased in both the experimental and contrast groups. This study showed that staff training can increase staff confidence in managing aggression in people with autism spectrum disorders.