Indigenous human disease caused by West Nile virus (WNV) was first identified in the United States in August 1999 in the greater New York City area.1,2 By the end of 2004, human WNV disease had been reported in all states except Maine, Washington, Hawaii, and Alaska,3- 8 and WNV transmission to humans had been documented by five routes: mosquito bites (principally from Culex spp.), blood transfusions, organ transplantation, transplacental transfer, and breastfeeding.1 During 1999-2005, a total of 19,525 cases of WNV disease in humans and 771 deaths were reported in the United States. In 2000, CDC first published guidelines for WNV surveillance, prevention, and control and created ArboNET, an electronic surveillance and reporting system. Beginning in 1999, WNV surveillance and prevention activities had been initiated in selected states and large cities through the CDC Epidemiology and Laboratory Capacity (ELC) cooperative agreements for emerging infectious diseases and subsequently expanded to all 50 states, six large cities/counties,* and Puerto Rico. In 2005, to assess the capacity of state and large-city/county health departments to conduct WNV surveillance, prevention, and control activities, the Council of State and Territorial Epidemiologists (CSTE), with assistance from the Association of Public Health Laboratories (APHL) and CDC, surveyed WNV programs in the 50 states and six large-city/county health departments. This report describes the results of that assessment, which indicated that all participating states and cities had well-developed surveillance and control programs for human, avian, equine, or mosquito WNV.