Vitamin C (ascorbic acid) has considerable antioxidant activity: it scavenges reactive oxygen species and may, thereby, prevent oxidative damage to important biological macromolecules, such as DNA, proteins, and lipids. Data concerning the influence of vitamin C on oxidative DNA damage are conflicting and some of the discrepancies can be explained by the different experimental methodologies employed. Data using biomarkers of oxidative damage of DNA bases in human lymphocytes in vitro have provided no compelling evidence to conclude that vitamin C supplementation can decrease the level of oxidative DNA damage. There are also no conclusive data from studies of strand breaks for a protective effect of ascorbic acid. The consumption of food rich in vitamin C (fruits and vegetables) appears more protective because it exerts more positive effects in decreasing oxidative DNA damage to human cells. Recent studies indicate that vitamin C is much more than just an antioxidant; it regulates the expression of some genes participating in apoptosis or DNA repair processes. The purpose of this review is to provide a summary of the role of vitamin C in oxidative DNA damage.