Key molecular properties are calculated for the 8 most common aflatoxins at the B3LYP/6-31 + G(d,p) level. Special attention is given the possibility of aflatoxins to generate reactive oxygen species (ROS). It is concluded that the excited triplet states of the aflatoxins have properties that make them very potent ROS generators, in addition to direct photoinduced addition reactions. The elevated toxicity of aflatoxin B1 is discussed in terms of its lower ionization potential, and the coincidence of higher lying triplet states with dominant lowlying singlet excitations, which enables rapid intersystem crossing and decay along the triplet channel to the T-1 state. (c) 2006 Elsevier B.V. All rights reserved.