Adsorption equilibrium data of water vapor on a commercially available activated alumina, Selexsorb-CDX, were measured by a static gravimetric technique. The relative humidity and temperature were varied between 0 % and 90 % and between (S and 35) C, respectively. The measured data were fitted to the dual mechanism adsorption potential (DMAP) equation. The pore structure of the adsorbent material was characterized by nitrogen adsorption and mercury intrusion measurements, The DMAP equation predicted that the first SO % of the total water adsorbed was held on the adsorbent by the combined action of chemisorption and physisorption, which was attributed to filling of the micropores and the first adsorbed layers in the mesopores. The remainder of the adsorbed water was attributed to capillary condensation in the mesopores. The heat of adsorption as a function of fractional loading was calculated using the fitted DMAP equation parameters in conjunction with the van't Hoff equation, with and without an assumption of the Clausius-Clapeyron equation. The two methods for the heat of adsorption calculation were in excellent agreement, differing by no more than 0.2 kJ . mol(-1). The reported experimental data and correlation parameters can be readily applied in the modeling, design, and optimization of dehumidification processes utilizing the Selexsorb-CDX activated alumina adsorbent used in this study.