Mycotoxins are toxic products secreted by microscopic fungi. They can contaminate products of vegetal origin consumed by humans and cattle, therefore secondary by humans. The most important mycotoxins are aflatoxins, hepatotoxic and hepatocarcinogenic, and ochratoxins, nephrotoxic and nephrocarcinogenic. The maximal authorized limits of aflatoxin contents in human and animal food-stuffs are very low (few microg/kg or fractions of microg/kg).