Oxidative DNA damage in peripheral white blood cell of smokers were estimated in accordance with the levels of 8-Hydroxydeoxyguanosine (8-OHdG) in nuclear DNA and the antioxidant status of these smokers' plasma was investigated in terms of the ex vivo oxidation resistance of plasma. In a survey of 12 smokers (4 women) aged 22 to 48, the mean level of 8-OHdG was 3.79+/-0.65 residue/10(6) dG (mean +/- S.D.) with a range from 2.83 to 4.62 residue/10(6) dG. These measurements showed approximately 1.6-fold inter-individual variations of 8-OHdG level in smokers. A higher level of 8-OHdG was found for smokers whose ex vivo plasma oxidation resistance was weak. Significant association is seen between oxidized bases in white blood cells and plasma oxidation resistance, whereas signs of any association with plasma concentration of alpha-tocopherol, ascorbic acid, bilirubin, and uric acid are weak and sporadic. These findings indicate that apparent heterogeneity exists among smokers in some sort of resistance to the oxidative effects of smoking.