Analytical predictions for first adsorption layer of water as a function of relative humidity in hydrophilic materials were developed using multilayer adsorption theories (BET and GAB). These predictions were compared with experimental values of bound water adsorbed by methylcellulose reported in a previous paper. A proper analysis method is proposed that improves the determination of the physical parameters employed by the GAB theory. The applicability of the GAB and BET adsorption models employed in the study of condensable vapors or gas condensation is discussed. (C) 2003 Elsevier Science Ltd. All rights reserved.