The proposed project is a study of the interaction of aflatoxins and ochratoxins with cellular macromolecules both in vivo and in vitro. During the first year, the interaction of aflatoxins B1, B2, G1 and G2 with tryptophan, and B2a with proteins and amino acids were studied. Tryptophan serves as an electron donor to form charge transfer complexes with the aflatoxins, whereas the amino groups of amino acids and proteins form a Schiff-base with aflatoxin B2a. In vitro studies on the interaction of ochratoxins with bovine serum albumin revealed that the conformation of the protein is important in such interaction. Ochratoxin A also interacts with arginase, thrombin catalase and deoxyribonuclease. In addition, a method for production of high specific radioactive 3H-ochratoxins, and a method for preparation of reduced aflatoxins B1 and B2 were developed.