After being awarded the 1954 Nobel Prize in Chemistry "for his research into the nature of the chemical bond and its application to the elucidation of the structure of complex substances", Linus Pauling turned his attention to a range of medical issues, including topics like the mechanisms of general anaesthesia or the molecular mechanisms of sickle cell anaemia, which he both discussed in his 1964 Lindau lecture (LINK). He also briefly worked on mental diseases. This brought him to the vitamins, some of which were evaluated as drug candidates for mental patients. What ensued was some of his probably most controversial work, which culminated in the claim that vitamin C megadoses (around 10 g per day) would be suited to treat cancer and support health in general. Pauling himself took at least 10 g of vitamin C per day for more than 20 years. Aged 93, he died of prostate cancer. Before his death, he claimed that vitamin C had delayed the onset of his disease significantly. In the present lecture, Pauling clearly outlines the rationale that led him to support vitamin C megadoses. He begins by pointing out the importance of vitamin C for collagen biosynthesis (collagen is a structural protein responsible for the integrity of skin, hair, muscles, tendons and other tissues) and hypothesizes that vitamin C could inhibit the metastasis of cancer by generally strengthening tissues due to improved collagen synthesis. His second argument concerns the curious fact that the vast majority of animals are able to biosynthesize vitamin C and are thus not dependent on an intake via food. Humans, primates, bats, guinea pigs are some of the exceptions. Pauling extrapolates that a typical animal weighing 70 kg would produce 10 g of vitamin C per day. This is much more than a human will normally take up via food, hence, according to Pauling, heavy supplementation is necessary. This line of thought is the source of his famous 10 g per day megadosage recommendation. However, to date (2013), it has not been proven that vitamin C megadoses are suited as a cancer therapy and the studies Pauling describes in his talk have been shown to contain systematic flaws. In this context, the remarks made towards the end of the talk are highly problematic. Based on the assumptions that (i) vitamin C helps to fight cancer by stimulating the immune system and that (ii) vitamin C can hence not act if the immune system is suppressed by chemotherapy, Pauling recommends to treat adult cancer patients with vitamin C only and to omit chemotherapy altogether. Luckily, this highly questionable recommendation was never adopted by conventional medicine.The Linus Pauling Institute at the Oregon State University, founded in 1973 by Pauling and colleagues, today distances itself from the claim that vitamin C is effective in cancer therapy and recommends a rather low daily intake of 400 mg based on the “currently available epidemiological, biochemical, and clinical evidence” [1]. David Siegel [1] http://lpi.oregonstate.edu/infocenter/paulingrec.html