Deoxynucleosides were reacted in a lipid peroxidation model system, emulsified hemin-ethyl linoleate, and the adducts thus produced were analyzed by HPLC. Substantial amounts of stable adducts were detected in the dA- and dC-reaction mixtures. The structures of the major dA and dC adducts, other than the known 4-oxo-2-nonenal adducts, were determined to be etheno-type adducts, with a C₆ side chain bearing an α-hydroxyl-group. These results suggested that the substance involved in adduct formation is 2,3-epoxyoctanal. This compound showed mutagenicity in Salmonella strains TA 100 and TA 104 without the S-9 mix. In addition, based on the structure of a minor dC adduct, another possibly involved mutagen, 4-oxo-2-octenal, was proposed. These mutagens may be formed during storage and cooking of food, or during digestion, and may be involved in human cancers.