The United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services (USDA APHIS WS), National Wildlife Research Center (NWRC) “Chemical Effects Database” is an internet-accessible and searchable database that contains bioassay data records for chemicals evaluated for repellency, toxicity, reproductive inhibition, and immobilization of higher vertebrates, and phytotoxicity. These data are of value for environmental risk assessment, conduct of toxicology studies, and the development of safe, effective, and responsible tools to manage vertebrate pest species that cause damage. Chemical screening studies were conducted from 1943 to 1987 by predecessors of the NWRC, and by the U.S. Geological Survey Patuxent Wildlife Research Center (PWRC), formerly the Patuxent Research Refuge (PRR) and part of the U.S. Fish and Wildlife Service. The screening activities were broadly divided into 2 phases. Data collected primarily at the PRR prior to 1960 are published in DeWitt et al. (1953) and Bowles et al. (1974). Research after 1960 was conducted at the Denver Wildlife Research Center (DWRC). Much of these data are also published and now accessible by searching the on-line “Chemical Effects Database” located on the NWRC website (http://www.aphis.usda.gov/wildlife_damage/nwrc/information_services/chemical_effects.shtml). The database search capabilities provide easy access to approximately 11,000 bioassay data records for nearly 2,000 chemicals.