In this work the Arrhenius parameters and heat of reaction for the esterification of acetic anhydride by methanol and the esterification of propionic anhydride by 2-butanol were determined using a CPA 202 reaction calorimeter (ChemiSens). Three reaction rate models were tested for each of the esterification reactions, two of which assumed autocatalytic behaviour. The autocatalytic models were based on a carboxylic acid dependency; acetic acid and propionic acid being side products in the reactions studied. The two catalytic models gave excellent fits to the experimental results thus indicating autocatalytic behaviour. (C) 2006 Elsevier B.V. All rights reserved.