The reaction of aflatoxin B-1 exo-8,9-epoxide with calf thymus DNA gives small quantities of the previously unknown adenine N7 adduct in addition to the well-characterized deoxyguanosine N7 derivative. The adenine derivative can also be prepared by the reaction of epoxide with an oligodeoxynucleotide and with poly(dAdT). The deoxyadenosine adduct is more labile than the deoxyguanosine adduct, undergoing loss of deoxyribose at ambient temperature. The adenine adduct was independently synthesized by reaction of the epoxide with the 3’,5’-biS(O-tert-butyldimethylsilyl) derivative of 2’-deoxyadenosine. The linkage to adenine was shown to be at N7 by NMR spectroscopy employing C-H heteronuclear correlations, (3)J(C-H) coupling constants, and an NOE between aflatoxin H9 and adenine HS. NMR spectroscopic studies were also carried out with 1-, 3-, 7-, and 9-methyladenines to establish guidelines for making assignments on the aflatoxin adduct. Aflatoxin adduction carried out in D2O gave deuterium substitution at the adenine 8 position in the product.