EJScreen is an environmental justice (EJ) screening and mapping tool that provides EPA with a nationally consistent dataset and methodology for calculating "EJ indexes," which can be used for highlighting places that may be candidates for further review, analysis, or outreach as the agency develops programs, policies and other activities. The tool provides both summary and detailed information at the Census block group level or a user-defined area for both demographic and environmental indicators. The summary information is in the form of EJ Indexes and Supplemental which combine demographic information with a single environmental indicator (such as proximity to traffic) that can help identify communities living in areas with greater potential for environmental and health impacts. The tool also provides additional detailed demographic and environmental information to supplement screening analyses. EJScreen displays this information in color-coded maps, bar charts, and standard reports. Users should keep in mind that screening tools are subject to substantial uncertainty in their demographic and environmental data, particularly when looking at small geographic areas, such as Census block groups. Data on the full range of environmental impacts and demographic factors in any given location are almost certainly not available directly through this tool, and its initial results should be supplemented with additional information and local knowledge before making any judgments about potential areas of EJ concern.