Ascorbic acid (Vitamin C) is an essential micro-nutrient, an outstanding antioxidant and an essential co-factor in different mammalian enzymic processes. There is considerable clin. attestation that, high dose of i.v. ascorbic acid can improve cancer patients with or without extant therapeutic involvements. Ascorbic acid in high i.v. doses serves as pro-oxidant and promotes the generation of hydrogen peroxide (H2O2) and other reactive oxygen species (ROS) with oxidative stress-induced toxicity selectively to cancer cells. This effect also hampers the bioenergetics and angiogenesis of malignant cells, resulting in cancer cell death. Large doses of ascorbic acid are safe and well-tolerated. On account of its antioxidant effect, ascorbic acid supplementation may be applied as an adjuvant with regular cancer therapy to minimize complications. Nevertheless, there is a necessity for further mechanistic studies and randomized controlled clin. trials to evaluate the benefit of ascorbic acid in the treatment of cancer.