The adsorption equilibria of water vapor on activated carbon and DAY zeolite were measured by a static volumetric method. The equilibrium experiments were conducted at (293, 313, 333, 353, and 373) K and pressures up to 3.4 kPa for activated carbon and 1.9 kPa for DAY zeolite. According to the classification of isotherms, the experimental data are correlated by the Dubinin-Serpinsky and Sips models for activated carbon as well as the Toth, UNILAN, and Sips models for DAY zeolite.