Oxidation and the production of free radicals are an integral part of human metabolism, and oxidative stress is related to many diseases, including cancer and heart disease. The use of biomarkers for oxidative stress may provide further evidence of a causal relationship between oxidative damage to macromolecules (DNA, lipids, and proteins) and cancer. A wide variety of functional assays, both in vivo and ex vivo, include various measures of DNA oxidation (oxidized DNA bases such as 8-OHdG, autoantibodies to oxidized DNA, modified comet assay), lipid oxidation (thiobarbituric acid-reactive substances, exhaled pentane/ethane, low-density lipoprotein resistance to oxidation, isoprostanes), and protein oxidation (protein carbonyls). The objective of this review is to discuss characteristics and methodologic issues for studies involving biomarkers of exposure to antioxidant nutrients and of oxidative stress status. This paper provides an overview on the current knowledge of oxidative DNA, lipid, and protein damage and cancer incidence.