Key features of an isothermal titration microcalorimeter (ITC) are described together with a general equation which forms the basis of the analysis of the calorimetric results. Recent applications of titration microcalorimetry to four subject areas concerned with the properties of aqueous solutions are reviewed. The four subjects covered are (i) pairwise enthalpic solute–solute interaction parameters in aqueous solution, (ii) deaggregation of micelles formed by ionic surfactants, (iii) protein–ligand interactions and (iv) adsorption of adsorbates on polymeric adsorbents.