The goal of the Natural and Accelerated Bioremediation Research (NABIR) Program is to provide the fundamental science to serve as the basis for the development of cost-effective bioremediation of radionuclides and metals in the subsurface at DOE sites. The focus of the program is on strategies leading to long-term immobilization of these contaminants in place, to reduce the risk to humans and the environment. The NABIR program encompasses both intrinsic bioremediation and accelerated bioremediation through the use of biostimulation (the addition of inorganic or organic nutrients). The program consists of four closely interrelated Science Elements, three Cross-Cutting Elements, and the Field Research Center (FRC). The Science Elements are Biogeochemistry, Biotransformation, Community Dynamics/Microbial Ecology, Biomolecular Science and Engineering. Cross cutting elements include Bioremediation and its Societal Implications and Concerns (BASIC), Integrative Studies, and Assessment (innovative method development). The NABIR program has established a Field Research Center on the U.S. Department of Energy Oak Ridge Reservation in Oak Ridge, Tennessee. The FRC is a focal point for integration of process level understanding and field research for the NABIR program. Scientific disciplines represented in the program include microbial physiology and ecology, molecular biology, geochemistry, hydrology, and mathematical modeling. Interdisciplinary research is strongly encouraged. The NABIR program does not support research on organic contaminants (with the exception of metal-chelator complexes) or on phytoremediation.