Chromium(VI) compounds produce a variety of DNA damage such as DNA single strand breaks, alkali-labile sites and DNA-protein cross-links in vivo and in cultured cells. Chromium(III) compounds bound to isolated DNA and proteins. Cr(VI) readily entered cell through general anion channels. In contrast, Cr(III) did not readily cross cell membranes. Inside cells Cr(VI) is reduced through intermediates to Cr(III) by cellular reductants. Reactive intermediates formed during intracellular Cr(VI) reduction might be responsible for some chromate genotoxicity. Ascorbic acid decreases chromate induced alkali-labile sites and chromium inhibition of glutathione reductase, but it enhances DNA-protein cross-links and cytotoxicity caused by this metal.