Cadmium is a widespread environmental and occupational pollutant and quercetin is a dietary flavonoid, which is reported to modulate the effects of many mutagens and carcinogens. We investigated the ability of cadmium chloride to induce DNA damage in human lymphocytes in the presence of quercetin using the alkaline comet assay. Cadmium chloride (5-150 muM) evoked dose-dependent DNA damage and quercetin at 50 muM decreased the extent of the damage. The lymphocytes exposed to cadmium chloride were able to remove their DNA damage within a time period shorter than 120 min. The cells treated with quercetin at 50 muM prior to exposure to cadmium required shorter periods of time to recover. Quercetin could chelate cadmium ions, scavenge free radicals produced by cadmium or regenerate cellular DNA-repair enzymes.