Mycotoxins have significant economic impacts in numerous crops, especially wheat, maize, peanuts and other nut crops, cottonseed, and coffee. The Food and Agriculture Organization has estimated that 25% of the world’s crops are affected by mycotoxins each year, with annual losses of around 1 billion metric tons of foods and food products. Economic losses occur because of: 1) yield loss due to diseases induced by toxigenic fungi; 2) reduced crop value resulting from mycotoxin contamination; 3) losses in animal productivity from mycotoxin-related health problems; and 4) human health costs. Additional costs associated with mycotoxins include the cost of management at all levels– prevention, sampling, mitigation, litigation, and research costs. These economic impacts are felt all along the food and feed supply chains: crop producers, animal producers, grain handlers and distributors, processors, consumers, and society as a whole (due to health care impacts and productivity losses). Estimates of the costs of mycotoxins in the United States vary: one report estimated $0.5 to $1.5 billion/yr and another estimated $5 billion/yr for the U.S. and Canada. Neither of these estimates included human health impacts or crop yield losses. Aflatoxins in maize in the U.S. have been estimated as a $225 million/yr impact, not including mitigation costs ($20-30 million/yr just for testing). Aflatoxins in U.S. peanuts were estimated to cause over $25.8 million in losses per year during 1993 to 1996, with most of the costs (nearly $23 million) being shouldered by the shelling segment of the industry. Grower losses were estimated at about $2.6 million per year. Losses associated with deoxynivalenol in the United States were estimated at $655 million/yr, with the majority of the losses in wheat. In developing countries, few estimates are available, but based on the elevated levels of aflatoxins regularly found in the developing world, it is likely that losses consistently exceed those occurring in the United States. As an example, losses due to aflatoxins in three Asian countries (Indonesia, Philippines, and Thailand) were estimated at $900 million annually. Reduced crop value is a significant component of the losses caused by mycotoxins. This affects crops entered into local trade as well as crops intended for export. In aflatoxin-outbreak years in the U.S., many producers are turned away by grain elevators and other buyers because their crop exceeds the 20 ppb limit. They are forced to accept a lower price on the local feed market, or even to dispose of their crop. Internationally, a standard limit of 4 ppb (adopting the European Union limit) for aflatoxins in peanuts would be estimated to cost about $450 million annually in lost exports. The impact of export losses is worsened by the situation in which developing countries, whose populations are most at risk for aflatoxin exposure, may be forced to export their highest quality maize and retain the poorer grain for domestic use. As maize grain is increasingly used to produce ethanol, the economic impact of mycotoxins does not decrease, and may actually increase. An important co-product of ethanol production is dried distillers’ grain and solubles (DDGS), which is sold as an animal feed component. Mycotoxins in the original grain become concentrated in the DDGS, resulting in an estimated $18 million impact per year for fumonisins in the U.S. swine industry. Losses to the swine industry may be lower because of grain monitoring by ethanol plants; in this case the economic impact of fumonisins in DDGS would be spread out among the swine industry, the ethanol industry, and maize producers. In order to maintain acceptable mycotoxin levels in DDGS, incoming grain should be strictly monitored, but this will certainly lead to higher costs for the ethanol plant and a loss of salability for mycotoxin-contaminated grain. Human health impacts of mycotoxins are the most difficult to quantify. It is clear that mycotoxins affect human health, especially aflatoxins in developing countries. These effects are due to acute (single exposure) toxicoses and immunosuppression by mycotoxins, as well as chronic (repeated exposure) effects. Outbreaks of aflatoxicosis in Kenya have led to hundreds of fatalities, even during the past decade. Over 98% of individuals tested in several West African countries were positive for aflatoxin exposure. Diseases modulated by mycotoxins accounted for 40% of lost disability-adjusted life years in a 1993 World Bank report on human health. Of the reported $900 million impact of aflatoxins in Southeast Asia, $500 million of the costs were related to human health effects. A report from the National Academy of Sciences concluded that mycotoxins probably contribute to human cancer rates, even in the United States. On a global scale, human health is the most significant impact of mycotoxins, with significant losses in monetary terms (through health care costs and productivity loss) and in human lives lost. Two recent outbreaks of mycotoxin poisoning underscore the impact of mycotoxins in human and animal health.