The mechanistic basis for the reactions occurring in irradiated foods must be understood if the chemical consequences are to be predicted and put into proper perspective. Of major concern are the levels of radiolysis products, their relation to food composition, and the influence of processing factors on their formation. By applying our radiation chemical knowledge, the information available are taken from model system studies and from analyses of food systems, discern the commonality, and then generalize. The initial radiolytic events are ionization and excitation and reaction of the cation radical, anion radical, and excited molecule formed. Most of the solvated electrons reacting with the metallo-protein should attach to the ring amino acids and the peptide carbonyl group. Several unimolecular reactions and bimolecular exchange and combination reactions can take place involving the radicals formed from the primary species that determine the spectrum of final products. Bimolecular combination reactions are relatively rapid and can lead to high molecular weight products.