A gas barrier and biodegradable multilayer material was processed with a paper substrate, chitosan, and carnauba wax. The first step consisted of the study of the chitosan coating to obtain a dense polymer layer at the paper surface. The influence of the molecular weight and the concentration of the chitosan solution were studied, and a chitosan coating of 7 g/m(2) was achieved, which led to interesting gas barrier properties in the anhydrous state. Nevertheless, the hydrophilic character of both cellulose and chitosan did not allow us to preserve these properties in the hydrated state. A layer of carnauba wax was then deposited on the chitosan face of the bilayer. Because of the hydrophobic character of this external layer, the water sorption in the multilayer decreased greatly, and CO2 and O-2 permeability coefficients lower than 0.5 barrer were obtained in the hydrated state. (c) 2005 Wiley Periodicals, Inc.