Chronic, severe irritability is common in childhood and is very impairing. Furthermore, childhood irritability predicts suicidality, social impairment, and depressive and anxiety disorders in adulthood. Focusing on both normative and pathologic development, we review the construct of irritability from its origins in aggression and disruptive behavior research to its contemporary relevance for affective psychopathology. We then describe two broad neurocognitive systems that show promise in differentiating irritable from nonirritable youths: aberrant processing of emotional stimuli and impaired context-sensitive regulation. We suggest behavioral, neurocognitive, and physiologic measures that may aid in studying severe irritability and assessing its therapeutics. Finally, we argue for therapeutic trials targeting severe irritability that address emotional aspects of irritability in addition to the associated disruptive behavior.