Impulsiveness has been studied as an aspect of personality and psychopathology for generations. There are longstanding disagreements about how to define it and whether it should be viewed as one construct or several. This article begins by briefly reviewing some earlier and some more recent work on impulsiveness. Several approaches have recently converged to focus on a distinction between impulsive reactions to emotion and impulsive properties that are not initiated by emotion. From this review, we turn to psychopathology. It is well known that impulsiveness is related to externalizing psychopathology, but some have concluded that a similar relation does not exist for internalizing psychopathology. A recent literature is described that challenges the latter conclusion, linking impulsive reactivity to emotion to both externalizing and internalizing aspects of psychopathology. Discussion then turns to emotion-related impulsiveness and other constructs to which it is conceptually and empirically related, reexamining whether other conceptual targets should be added to the discussion. The article closes with a consideration of how important it is to continue to remain open to new conceptual perspectives. (PsycINFO Database Record (c) 2018 APA, all rights reserved).