The purpose of this work is to investigate the entropy generation in a laminar, conducting liquid flow inside a channel made of two parallel heated plates under the action of a transverse magnetic field. The flow is considered fully developed. The effect of heat generation by viscous dissipation is included in the analysis. The influence of the applied magnetic field and the viscous dissipation on velocity, temperature and entropy generation is examined. (c) 2006 Elsevier Ltd. All rights reserved.