Isothermal titration calorimetry (ITC) is now an established and invaluable method for determining the thermodynamic constants, association constant and stoichiometry of molecular interactions in aqueous solutions. The technique has become widely used by biochemists to study protein interaction with other proteins, small molecules, metal ions, lipids, nucleic acids and carbohydrates; and nucleic acid interaction with small molecules. The drug discovery industry has utilized this approach to measure protein (or nucleic acid) interaction with drug candidates. ITC has been used to screen candidates, guide the design of potential drugs and validate the modelling used in structure-based drug design. Emerging disciplines including nanotechnology and drug delivery could benefit greatly from ITC in enhancing their understanding and control of nano-particle assembly, and drug binding and controlled release. Copyright © 2010 John Wiley & Sons, Ltd.