We investigated the combined effects of low-energy electron irradiation and Fe³ ion on DNA damage. We used lyophilized pBR322 plasmid DNA films with various concentrations (0 ∼ 7 mM) of Fe³ ions and irradiation with monochromatic, low-energy 3 or 5 eV electrons for these studies. DNA-Fe³ films were recovered and analyzed by agarose gel electrophoresis to identify and compare the effects of Fe³ ions and/or low-energy electrons alone or in combination on DNA damage. In nonirradiated DNA-Fe³ films, there was little DNA damage observed (less than 10% of the total DNA loaded on the gel appeared damaged) for Fe³ ion up to 7 mM concentration. In irradiated DNA films without Fe³ ions, there was also very little DNA damage observed (less than 3% of the total DNA loaded on the gel appeared damaged). However, when DNA-Fe³ films, were irradiated with low-energy electrons, DNA damage was significantly increased compared to the sum of the damage caused both by either Fe³ ion or low-energy electrons irradiation alone. We proposed that both DEA and/or electron transfer processes might play a role in the enhanced DNA damage when DNA-Fe³ films were irradiated by low-energy electrons.