This paper proposes an integral method that uses local heating rates to evaluate the activation energy dependence on the extent of conversion. The method leads to consistent results with those from a differential isoconversional technique while regular integral isoconversional technique results in systematic errors in the activation energy with the extent of conversion. The method is validated from (1) simulated thermal analysis curves for a single reaction model, (2) simulated thermal analysis curves involving in two parallel reactions, and (3) non-isothermal dehydration of calcium oxalate monohydrate. (c) 2005 Elsevier B.V. All rights reserved.