The area of isothermal titration microcalorimetric (ITC) studies on solution systems involving nucleotides is reviewed. 62 references are cited. About 25 ITC studies on nucleotide systems have been published during the last two decades. The main part (ca 95%) of these papers deal with nucleotide-protein interactions and one paper involves nucleotide-nucleotide binding studies. The results of such studies include stoichiometry, the (concentration) binding constant, Kb, the enthalpy of binding, ΔHb° , the standard Gibbs free energy of binding, ΔGb° , the entropy of binding, ΔSb° , and the heat capacity of binding at constant pressure, ΔCp° . Information on proton uptake / release upon complex formation, modeling on binding cooperativity and conformational change can also be derived. In binding studies, calorimetric ΔCp° and ΔHb° data have been used to model the change in apolar and polar solvent accessible surface areas, ΔASAnpol and ΔASApol, respectively.