Mycotoxins produced by Aspergillus ochraceus, Aspergillus spp., and Penicillium viridicatum. They can be categorized as ochratoxin A, B, and C and 4-hydroxyochratoxin A. Ochratoxin A, the most important ochratoxin, is a fairly stable substance that is not easily metabolized. It is a potent hepatotoxin (in rats, ducklings, and Babcock cockerels) and a nephrotoxin (in rats and pigs). Theprimary target organ is the developing central nervous system (CNS). Furthermore, it was reported to be teratogenic in mice and rats, whereas it was noncarcinogenic to rats by both oral and subcutaneous administration. Ochratoxin A production in cereals is favored under humid conditions at moderate temperatures. Occurrence of ochratoxin A has been reported in grains and, following transfer, in the organs and blood of a number of animals, especially pigs.