beta-Glucans of Agaricus brasiliensis fruiting bodies in different stages of maturity were isolated and characterized by FTIR and NMR. These fractions had greater amount of ( 1 --> 6)-beta-glucan and the (1 --> 3)-beta-glucan increased with fruiting bodies maturation. Yields of beta-glucans increased from 42 mg beta-glucans g(-1) fruiting bodies ( dry wt) in immature stage to 43 mg g(-1) in mature stage with immature spores, and decreased to 40 mg g(-1) in mature stage with spore maturation. Mature fruiting bodies, which included these glucans, have potential therapeutical benefits for use in nutraceutical products.