In a single-dosing crossover study, we investigated the ability of apple fruit consumption to protect human lymphocytes against peroxide-induced damage to DNA. Six healthy, non-smoking male volunteers were placed for 2d on an antioxidant-poor (AP) diet. After 48h of AP diet, the volunteers were required to consume a homogenate obtained from 600g of red delicious unpeeled apples or water (500 ml); blood samples were collected 0, 3, 6 and 24 h post-consumption. To evaluate whether the apple intake was sufficient to restore resistance of DNA to oxidative damage, for each subject at any time point the plasma total antioxidant activity, reactive oxygen species (ROS) formation and induction of micronuclei (MN) in isolated lymphocytes following hydrogen peroxide (H2O2) treatment were measured. Results indicated a significant inhibition (58%, P <0.05) of H2O2-induced MN frequency in the plasma samples collected at 3 h after apple consumption, as compared with plasma samples collected at 0 h (4.17 (SD 1.83) v. 9.85 (SD 1.87) MN/1000 binucleated (BN) cells, respectively). A gradual return towards the value observed at 0 h was recorded starting from 6 to 24 h. MN frequency induced by H2O2 was significantly influenced by plasma total antioxidant activity (r = -0.95, P <0.05) and by the increase of intracellular ROS formation (r = 0.88, P <0.05). These findings suggest that the consumption of whole apple provides a useful dietary source of active scavengers to protect cells and tissue from oxidative stress and related DNA injury.