Dr. STEPHEN S. FRANCIS, of the Center for Integrative Research on Childhood Leukemia and the Environment at the University of California Berkeley, discusses whether infectious agents may have contributed to a possible cluster of childhood leukemia cases in Fallon Nevada. A role for an infectious agent, in this case a virus, is suggested because there was a spike in cases of childhood leukemia in US military dependent populations at around the same time; Fallon had a naval air station that brought military personnel into the town; and the locations where children with the disease lived tended to be in areas where transmission by mosquitoes might occur. This was part of a symposium organized by the Office of Environmental Health Hazard Assessment oehha.ca.gov the Pediatric Environmental Health Specialty Unit at UCSF coeh.berkeley.edu and the Center for Integrative Research on Childhood Leukemia and the Environment at the University of California Berkeley circle.berkeley.edu. Research funding is from the National Institute of Environmental Health Sciences and US EPA. Views expressed are not those of these agencies.