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Cr (VI)-containing compounds are well-established carcinogens, although the mechanism for chromium-induced carcinogenesis is still not well understood. The reduction of Cr(VI) to its lower oxidation states, par-ticularly Cr (V) and Cr (IV), is an important step for the production of chromium-mediated reactive oxygenspecies (ROS). The persistent oxidative stress during the reduction process may play a key role in the mecha-nism of Cr(VI)-induced carcinogenesis. This paper summarizes recent studies on (1) the reduction of Cr (VI) to Cr (III) occur by a multiplicity ofmechanisms depending on the nature of reducing agents including ascorbate, diol-and thiol- containing mole-cules, certain flavoenzymes, cell organelles, intact cells, and whole animals; (2) free-radical production withemphasis on hydroxy radical generation via Fenton or Haber-Weiss type reactions; and (3) free radical-inducedcellular damage, such as DNA strand breaks, hydroxylation of 2′-deoxyguanosine, and activation of nucleartranscription factor κB.