This overview for the special issue of Health Education & Behavior on "Health Disparities and Social Inequities" briefly outlines the transdisciplinary (TD) approach to research and examines the scope of TD science. The need to embrace basic science as well as several domains of applied research is discussed along the TD "pipeline" from discovery to development to delivery to policy. The overview concludes with selected examples of the emerging TD science of disparities. One central challenge for a TD approach is the need to strengthen what is being called "the science of dissemination" along with improving the "dissemination of evidence-based science."