The DSM-5 ADHD and Disruptive Behavior Disorders Work Group recently outlined a research agenda designed to support possible revisions to the diagnostic criteria for oppositional defiant disorder (ODD) and conduct disorder (CD). Some of the areas in need of further investigation include (a) examining the clinical utility of the current diagnostic system in girls, (b) further clarifying the developmental progression from ODD to CD, (c) determining whether facets of ODD symptoms can help explain heterotypic continuity and enhance predictive validity, (d) evaluating the clinical utility of a new subtyping scheme for CD on the basis of the presence of callous-unemotional traits, and (e) comparing the clinical utility of dimensional versus categorical conceptualizations of ODD and CD. This special section was organized in an attempt to provide data on these issues using a diverse array of longitudinal data sets consisting of both epidemiological and clinic-based samples that collectively cover a large developmental span ranging from childhood through early adulthood.