The understanding of internalizing disorders in young children has lagged behind advances in our understanding of other areas of psychopathology in this age group. One factor contributing to the relatively slower progress in this domain might be that, as a group, internalizing disorders tend to be viewed as less problematic by parents, teachers, and other caregivers. This may be related to the fact that such disorders are most often characterized by quiet, internal distress sometimes referred to as "intropunitive," rather than overtly, socially negative, or disruptive behavior. Such features may also make these disorders more difficult to detect in the very young who have less well-developed verbal skills in general and specifically an even more limited capacity to describe internal feeling states.Despite these impediments, a major shift, and advance in this area, has been the study of more discrete differentiated disorders instead of lumping of all internalizing symptoms into one broad category of the two-dimensional internalizing versus externalizing taxonomy of childhood psychopathology. This shift in the conceptualization and categorization of psychopathology, although still an area of considerable debate, has allowed systematic investigation of diagnostic nosologic classifications used in older children and adults and has contributed to our understanding of the differentiation between mood and anxiety disorders in early childhood and differences between preschoolers and school-age children. In older children, some investigations have provided data that dispute this distinction, suggesting that some anxiety disorders (eg, generalized anxiety disorder) should be categorized with major depressive disorder (MDD).1 , 2 However, several investigations in young children have supported a meaningful distinction between mood and anxiety disorders in general.3 , 4 The question of whether to lump or split mood and anxiety disorders, and how to split them in early childhood, remains a relatively empirically unexplored area in need of further study.The shift to a categorical and more differentiated view of mood and anxiety disorders in early childhood has also created a gap in our ability to link this newer literature to the large and rich older body of literature on young children that used these broader dimensional measures of psychopathology.5 -7 As in other areas of young child psychopathology, the recent development of age-appropriate measures of psychopathology has catalyzed this area of research, with findings moving beyond the traditional two-dimensional taxonomy as offered by the widely used Child Behavior Checklist (CBCL). In addition to the