This study is focused on the entropy production due to laminar forced convection in the entrance region of a concentric cylindrical annulus. The present hydrodynamic and temperature fields are obtained numerically. Local entropy generation distributions are obtained based on the resulting velocity and temperature fields by solving the entropy generation equation. The effect of different flow parameters on thermal, viscous, and total entropy generation is studied for different thermal boundary conditions. Moreover, the effect of radius ratio on the entropy generation is investigated. Entropy generation was found to be inversely proportional to both Reynolds number and the dimensionless entrance temperature. The results also show that increasing Eckert number and/or the radius ratio will increase the entropy generation. Finally, it is found that thermal entropy generation is relatively dominant over viscous entropy generation. (C) 2003 Elsevier Ltd. All rights reserved.