The objective of this report was to conduct a search of the published literature on the use of supplement forms of the antioxidants, vitamin C, vitamin E, and coenzyme Q10, for the treatment and prevention of cancer and, on the basis of that search, to evaluate the evidence for the efficacy of these antioxidants. A broad search revealed sufficient literature to support a detailed review of the use of two of these antioxidants for cancer. Patients with cancer commonly try a variety of nontraditional treatments that fit the broad category known as Complementary and Alternative Medicine (CAM). However, evidence is lacking for the effectiveness of most CAM therapies for cancer. Among the CAM therapies publicized by the popular press for cancer treatment are several supplementary antioxidants: vitamin C, vitamin E, and coenzyme Q10. It has long been argued that the adequacy of the vitamin supply to cells and tissues influences the development, progress, and outcome of cancers. A major challenge to the integrity and function of cells and tissues is thought to come from the uncontrolled formation of free radicals. Free radicals may, alone or in combination, attack cell membranes and DNA. The body has evolved antioxidant defenses to protect against free radical induced damage. It is postulated that the antioxidant vitamins E and C and coenzyme Q10 are potentially involved in these antioxidant defenses and that some diseases might be prevented by increasing intake of antioxidants, either through increasing the dietary intake of antioxidant-rich foods or taking antioxidant supplements. However, it should be noted that while free radicals have been implicated in over 100 human diseases, this implication does not constitute proof of their role in disease formation or that preventing the formation or function of free radicals can prevent or cure disease.