This review summarizes the recent knowledge about the positive effect of betaglucans on human health. Beta-glucans are polysaccharides occurring in the bran of cereal grains (barley and oats and to a much lesser degree in rye and wheat, in amounts of about 7%, 5%, 2% and less than 1%, respectively), the cell wall of baker's yeast, certain types of fungi, and many kinds of mushrooms. The differences between soluble and insoluble beta-glucans are significant in regards to application, mode of action, and overall biological activity. A growing body of science indicates that beta-glucans promote health in a number of important ways. Beta-glucans have been studied for their hypocholesterolemic effects; these mechanisms include: reducing the intestinal absorption of cholesterol and bile acids by binding to glucans; shifting the liver from cholesterol syntheses to bile acid production; and fermentation by intestinal bacteria to short-chain fatty acids, which are absorbed and inhibit hepatic cholesterol syntheses. Several studies have also shown that oat beta-glucans blunt the glycemic and insulin response. Moreover, beta-1,3-glucans improve the body's immune system defense against foreign invaders by enhancing the ability of macrophages, neutrophils and natural killer cells to respond to and fight a wide range of challenges such as bacteria, viruses, fungi, and parasites. Finally, there is renewed interest in the potential usefulness of beta-glucan as a radioprotective drug for chemotherapy, radiation therapy and nuclear emergencies, particularly because glucan can be used not only as a treatment, but also as a prophylactic.