On May 24-26, 2004, U.S. Environmental Protection Agency (EPA) New England, EPA's Office of Research and Development (ORD) and Boston University's School of Public Health (BUSPH) co-sponsored the Science of Environmental Justice (SEJ) Working Conference in Boston, Mass. The title of the conference was: Science to Action: Community-based Participatory Research and Cumulative Risk Analysis as Tools to Advance Environmental Justice in Urban, Suburban and Rural Communities. The conference provided an interactive, educational forum and joined together stakeholders from across the country to discuss current efforts in community-based participatory research (CBPR) and cumulative risk analysis that are helping to assess, address and resolve environmental and public health risks in urban, suburban and rural areas. The conference presented methods and facilitated discussion regarding needs and opportunities for EPA and other research entities to invest in innovative scientific paradigms in order to better protect human health and the environment in environmental justice communities. The conference resulted from the awareness that many vulnerable communities and populations (i.e., communities of color, low-income communities, children, the elderly and subsistence fishers) face higher exposures or risks to their overall health and well-being from environmental sources. Traditional research and risk assessment methods have played an important role in reducing significant environmental health risks to the American public, but must be improved to better protect vulnerable populations and to further reduce residual risks. Achieving environmental justice for every community requires a different scientific approach, one that is rooted in communities and that can incorporate people's social stressors, economic stressors, unique needs and vulnerabilities. This conference proposed that community-based participatory research and cumulative risk assessment can form the core of this new science of environmental justice and explored, in-depth, the definitions, successes, needs and long-term opportunities for integrating this approach into EPA's research agenda.