Intermittent explosive disorder (IED) is characterized by recurrent episodes of impulsive, uncontrollable aggression out of proportion to the severity of provoking agents. Few epidemiological studies have been carried out on the prevalence and correlates of IED. Data are reported here from the most recent and largest of these studies: the U.S. National Comorbidity Survey Replication (NCS-R) and the World Health Organization World Mental Health (WMH) surveys. These studies show that IED is a commonly occurring disorder that typically has an early age of onset, a persistent course, and strong comorbidity with a number of other usually secondary mental disorders. This disorder is almost twice as common among men as women. It is often associated with substantial distress and impairment. However, only a minority of people with IED obtain treatment for their uncontrollable anger. This combination of features makes IED an ideal target for early detection and intervention aimed at secondary prevention of anger attacks as well as primary prevention of secondary disorders.