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The use of organophosphorus and carbamate pesticides has increased markedly during the past two decades. Currently, more than 100 different organophosphorus and carbamate chemicals are registered as the active ingredients in thousands of different pesticide products in the United States. More than 160 million acre-treatments of these pesticides are estimated to be applied to agricultural crops and forests each year. Clearly, these two groups of chemicals constitute a major portion of all pesticides used today. Organophosphorus and carbamate compounds have histories dating back long before their use as pesticides. Carbamates were developed during investigation of "ordeal" poisons used in Africa and made from the calabar bean, which contains the only known naturally occurring carbamate ester (Kuhr and Dorough 1976). The insecticidal activity of carbamates was discovered in 1931 and developed in the mid-to-late 1940's. Large quantities were being produced and used by the late 1950's (Kuhr and Dorough 1976). Although much research on organophosphorus compounds was done in the 19th century, the insecticidal activity of these chemicals was not discovered until 1937 (Eto 1974). In Germany, during World War II, the compounds were rapidly developed as insecticides, and during the 1950's the commercial use of organophosphates expanded markedly (Eto 1974). Presently, organophosphorus and carbamate pesticides are used as insecticides, herbicides, nematicides, acaricides, fungicides, rodenticides, and bird repellents throughout the world. The discovery that organochlorine pesticides, such as DDT, are highly persistent, bioconcentrate in food chains, and can severely affect whole populations or species of wildlife has led to bans and use restrictions (Stickel 1975). The decreased use of organochlorine pesticides has further expanded the market for the less-persistent organophosphates and carbamates (Murphy 1975: Stickel 1975). Today, organophosphorus and carbamate pesticide use is widespread On agricultural crops, rangelands, forests, and wetlands, and undoubtedly exposes many wildlife species to chemical hazards. Organophosphorus compounds represent the largest group of insecticides known (McEwen and Stephenson 1979). During the past decade, there has been an increase in the number of reports of wildlife die-offs related to organophosphorus and carbamate pesticide use. This handbook summarizes available information on organophosphorus and Carbamate pesticides in the wildlife toxicology literature and relates those data to potential hazards to wildlife by examining toxicity, environmental persistence; and use patterns of the pesticides included.