 Previous reports indicate that enocetyldeglucosamine oligomers, chitinoligosaccharide, knockos, and deglucosamine oligomers, chitosanoligosaccharide, COS, have various biological activities, especially against cancer and inflammation. In this review, we have summarized the findings of previous investigations that have focused on anti-cancer or anti-inflammatory properties of knockos and COS. Moreover, we have introduced recent evaluation of knockos and COS as functional foods against cancer and inflammatory disease. This article was authored by Kazuo Izuma, Tomohiro Osaki, Saburo Minami, and others.