Contamination of vegetable raw materials such as oil hearing crops, corn, rice, teat, and barley with mycotoxins, i.e. toxic and carcinogenic metabolites of microscopic fungi was reported from many countries. According to national legislations the content aflatoxins B must not exceed 2.5-20 ug/kg. Most countries, however, have not yet arranged a total supervision of contamination of grain and oil-bearing crops with aflatoxins and other mycotoxins. More often than not there is only a selective supervision of grain batches which have external signs of the development of microscopic fungi, or which have been stored in unfavorable conditions.