In this paper, heat source modelling of a microwave reactor is carried out thanks to electromagnetic simulation software HFSS(R). Thermal modelling of a chemical reactor under microwave irradiation represents an effective way to anticipate this type of heating. In the case of heterogeneous medium, controlling catalyst heating is essential for homogeneous heating and industrial applications. In a simplified case, modelling results are compared with experimental measurements and found to be in accordance with one another. In a second section, a new continuous flow microwave reactor under pressure is presented. The system can receive fixed, fluidised or circulating bed. Hydrogenation of nitrobenzene over supported palladium is performed. (C) 2004 Elsevier B.V. All rights reserved.