Isothermal microcalorimetry is a powerful tool in studies of organic reactions in solution. Both reaction kinetics and thermodynamic parameters at a single temperature are conveniently derived by this technique. Some applications of batch microcalorimetry in reaction mechanistic studies are reviewed. These include kinetic and thermodynamic studies of aromatization reactions of biologically interesting oxides, hydrates of aromatic hydrocarbons and studies of complex reactions and equilibria. Copyright © 2002 John Wiley & Sons, Ltd.