The Office of AIDS Research (OAR), located within the NIH Office of the Director, coordinates the scientific, budgetary, legislative, and policy elements of NIH AIDS research. The NIH represents the largest and most significant public investment in AIDS research in the world. Our response to the epidemic requires a unique and complex multi-institute, multi-disciplinary, global research program. Perhaps no other disease so thoroughly transcends every area of clinical medicine and basic scientific investigation, crossing the boundaries of nearly every Institute and Center (IC). This diverse research portfolio demands an unprecedented level of scientific coordination and management of research funds to identify the highest priority areas of scientific opportunity, enhance collaboration, minimize duplication, and ensure that precious research dollars are invested effectively and efficiently. OAR sets the trans-NIH scientific priorities for this large and diverse program, which is conducted or supported by nearly every NIH Institute and Center.