In this study for the first time temperature dependent terahertz pulsed spectroscopy was performed on a pharmaceutical drug. The polymorphic conversion process of carbamazepine form III to I was studied at varying temperatures. Furthermore, the solid-state transformation at isothermal conditions below the melting point of carbamazepine was investigated. The ability to study solid-state reactions with terahertz pulsed spectroscopy could be demonstrated. (c) 2005 Elsevier B.V. All rights reserved.