Isothermal heat conduction microcalorimetry is a technique which can be used to study very many physical and chemical processes. The experimental yield can potentially give information on thermodynamics of the process, kinetics (mechanism) and analysis. It is argued that with careful experimental design, and experienced data interpretation this technique is an extremely valuable tool for pharmaceutical scientists. The existing literature is discussed in terms of microbiological investigations, tissue culture studies, physical pharmacy (including immersion, adsorption, crystal properties, dissolution and targeting), and chemical stability studies.