Ochratoxin A (OA) is a mycotoxin produced by certain species of storage fungi of the Penicillium and Aspergillus genera. Toxin production by these fungi is influenced by species and even strain of fungi, time and temperature of incubation, moisture content of substrate, and type of substrate. OA has been shown to occur in various grains, cereals and other plant products, animal feeds, meats, and human tissues in countries throughout the world. Of interest is the discovery of OA in a high percentage of blood from humans in Germany. OA is acutely toxic to many different animals and in addition to being a nephrotoxin, it is a hepatotoxin, a teratogen, a very potent carcinogen, possibly a mutagen, and an immunosuppressive agent. OA is rapidly absorbed throughout the entire gastrointestinal tract and distributes itself in the body as a two-compartment open model and has a particular high affinity for serum albumin. OA is hydrolyzed by the intestinal microflora into nontoxic compounds (7-carboxy-5-chloro-8-hydroxy-3,4-dihydro-3R-methylisocoumarin (Oα) and phenylalanine). It is excreted as either OA, hydroxylated OA, or Oα in both the urine and feces. OA appears to exert its toxic effect by promoting an increased level of lipid peroxidation, by inhibition of an amino acylation reaction, and possibly by conversion into metabolites that are capable of binding DNA. These in turn cause other secondary effects associated with OA. It would appear that this compound presents a true potential hazard for humans as its occurrence is wide spread and it is highly carcinogenic.Key words: ochratoxins, ochratoxin A, metabolic effects.