The equilibrium moisture sorption isotherms of sweetpotato at temperatures of 5-50 degrees C and moisture content range of 8-30% (d.b.) were determined by means of a water activity meter. Out of the four equilibrium sorption models that were evaluated, the Hasley equation gave the best fit to the sorption data. The Hasley equation was further used to estimate the thermodynamic functions (heat of vaporization, differential entropy, enthalpy-entropy compensation, net integral enthalpy and entropy) of sweetpotato. The heat of vaporization and the differential entropy decreased with moisture in an exponential fashion. The maximum net integral enthalpy and the minimum net integral entropy were respectively obtained to be 418.94 kJ/kg and - 1.13 kJ/kg K. (c) 2005 Elsevier Ltd. All rights reserved.