The studies on experimental animals (guinea pigs, monkeys, fish) have confirmed the important role of ascorbic acid deficiency in the development of hypercholesterolemia and atherosclerosis, but the clinical experience is not quite uniform. Metaanalyses of randomized controlled trials performed on subjects without established vitamin C-deficiency conclud that the evidence of the presence or absence of benefits derived from the ability of ascorbic acid to prevent cardiovascular diseases is not sufficient. This review is an outline of numerous clinical, epidemiological and prospective studies that have found a positive role of vitamin C in the prevention of atherosclerosis. If we admit the possibility that vitamin C deficiency is a significant risk factor of atherogenesis, due to ethical reasons it is impossible to perform long-term controlled trials on subjects with proved vitamin C deficiency, to recommend them not to change their nutrition and lifestyle, and to administer placebo to the control group. Therefore the proof of atherogenic effect of chronic vitamin C deficiency is limited to indirect evidence only. In this review many new data on the positive effects of ascorbic acid on human cardiovascular system are summarized and the mechanisms of its protective influence on blood vessels are discussed (Fig.5, Ref. 45). Full Text (Free, PDF) www.bmj.sk.