The thermodynamic parameters (K, Delta H, Delta G, Delta S) for the complexation equilibrium of citric acid with beta-cyclodextrin (beta CD) in aqueous solution (1:1 stoichiometric reaction) have been determined by calorimetry at 298 and 308 K. The apparent solubility and the percentage of complexed beta CB are calculated for various citric acid concentrations (from 0 to 1 moll(-1)).