Intermittent explosive disorder (IED), a DSM-IV-TR disorder characterized by significant acts of aggression and violence, is being increasingly recognized as a prevalent and chronic disorder. Given the personal, social, and economic costs associated with IED, there is a clear need for well-validated assessment measures and efficacious treatments. However, there are currently no published, well-validated diagnostic measures of IED. With regard to treatment, preliminary evidence from a few randomized clinical trials suggests that selective serotonin reuptake inhibitors and cognitive behavioral psychotherapy may be effective in treating IED. However, more research is needed before either can be considered an empirically supported treatment for IED. In this chapter, we discuss (1) challenges in developing reliable and valid assessments for IED and (2) issues relevant to developing and testing psychological and pharmacological treatment interventions for IED.