Irritability has recently become a major focus of interest for clinicians and nosologists alike, and its position in the upcoming DSM-5 is currently debated. However, research on irritability has only recently started emerging. Here, I review the recent findings on irritability and its differentially strong relationship to depressive and generalised anxiety disorders compared to disruptive behaviours. Furthermore, I examine the importance of irritability in the recent debate about bipolar disorder in children and adolescents and discuss findings from research into severe mood dysregulation. I next address the relevance of irritability to the two core aims of developmental sensitivity and dimensionality. Finally, I critically discuss the recently proposed putative DSM-5 category of temper dysregulation disorder with dysphoria and make suggestions about future research directions.