WebDMAP is a web-based Geographic Information System (GIS) software designed to generate smoothed, continuous maps of crude or age-adjusted disease rates. WebDMAP provides advanced spatial analysis, GIS, and visualization methods in an easy-to-use, web-based analysis system designed specifically for users with little experience in spatial analysis methods or GIS software. WebDMAP is built using free, open-source products and is available as free, open-source software.