The Research Domain Criteria (RDoC) project is a framework for studying domains of biological and behavioral function that cut across traditional psychiatric diagnostic boundaries with the long-term objective of creating a new nosology based on specific biobehavioral measures. The initial aim is to provide a framework to drive clinical research. One goal of RDoC is to facilitate the development of biomarkers that could eventually be used for practical clinical diagnostic purposes and allow the development of new treatments targeting specific mechanisms of mental illness. In this entry, RDoC, its development, and the ways that it may evolve are described.