Complex formation of native and hydroxypropylated alpha-, beta- and gamma-cyclodextrins with benzoic acid in water was studied by means of calorimetry of solution at 298.15 K. The 1:1 complexes are formed with alpha- and beta-cyclodextrins, while 1:2 binding stoichiometry was observed for gamma-cyclodextrins. Thermodynamic parameters of complex formation of hydroxypropylated cyclodextrins were determined for the first time and analyzed. Comparison of binding affinity of native and modified cyclodextrins was carried out. (C) 2011 Elsevier B.V. All rights reserved.