Technical Abstract: Mycotoxins are compounds produced by fungi (or molds) that are poisonous to animals. Poisonous metabolites produced by mushrooms and yeasts are not included in this group. Strictly defined, mycotoxins are natural products produced by fungi that evoke a toxic response in higher vetebrates and other animals when fed at low concentrations. Some mycotoxins have multiple effects and also may be phytotoxic or antimicrobial. Mycotoxins, however, are not grouped with antibiotics, compounds which also may be produced by fungi but have microorganisms as the target species. Mycotoxins are not required for the growth of the producing fungus and, therefore, are considered secondary metabolites. Presumably, these compounds play some role in the ecology of the fungus, but their function has not been clearly defined. Many mycotoxins have been characterized and they show significant diversity in their chemical structures and biological lactivity. Further, many fungi produce multiple families of mycotoxins.