CDC, in collaboration with HealthMap, has created a new online tool for displaying global dengue activity. The interactive DengueMap shows areas where CDC considers dengue to be endemic and sites of recent, location-specific reports of disease. Unlike the CDC map that is compiled every 2 years for the CDC Travelers' Health Yellow Book to characterize general dengue risk based on traditional public health data sources, HealthMap reports are updated hourly and include both professional sources, such as the World Health Organization and ProMED-mail, and informal sources such as local media reports. Combined, these data provide a more dynamic and immediate picture of where transmission of dengue viruses might occur and where disease is actually occurring. DengueMap is available at http://healthmap.org/dengue and http://www.cdc.gov/dengue. Additional information regarding HealthMap is available at http://healthmap.org.