Some traditional Chinese medicinal seeds and fruits are well known for theirantioxidant properties. This research aims to investigate whether Fructus Lycii, FructusSchisandrae Chinensis, Fructus Ligustri Lucidi and Semen Cuscutae protect DNA fromoxidant challenge by hydrogen peroxide (H2O2). The standard comet assay was used toassess the genoprotective effect of these medicinal herbs. Blood was taken from three healthyadults, aged from 36 to 42. Lymphocytes were isolated and treated with different concentrationsof aqueous herbal extracts, while controls were treated with phosphate bufferedsaline. The lymphocytes were stressed with 50 'M H(2)O(2). Treated cells were embedded inagarose and layered on slides. These sandwiched lymphocytes were lysed and afterwardssubjected to an electric field in an alkaline environment. Damaged DNA was pulled out fromthe nucleus towards the positive electrode as a comet tail; its density was related to the degreeof DNA damage. Finally, the slides were stained with fluorescence dye and tails werevisually scored for 100 cells. The experiment was repeated three times and DNA damage intreated cells was compared to the controls. There was no statistical difference in DNAdamage among the herb treated cells and untreated cells in the comet assay. Our datademonstrated that the selected medicinal herbs did not show in vitro DNA protection in thecomet assay against oxidant challenge.