Autoxidation of linoleic acid leads to four major products: 9-hydroperoxy-10-trans-12-cis-octadecadienoic (1), 9-hydroperoxy-10-trans-12-trans-octadecadienoic (2), 13-hydroperoxy-9-cis-11-trans-octadecadienoic (3), 13-hydroperoxy-9-trans-11-trans-octadecadienoic (4) acids. The trans,cis:trans,trans product ratio (1 + 3:2 + 4) is dependent upon temperature, the concentration of linoleic acid undergoing peroxidation, and the presence of cosubstrates in the medium. To elucidate these effects, theoretical studies of linoleic acid peroxidation have been undertaken using absolute reaction rate theory. As a test of the theoretical model, the estimated rate constants have been employed in computer simulations of the experimental reaction systems. Calculated temperature, concentration, and cosubstrate effects are found to be in good qualitative agreement with experiment.