Heat transfer in a rotating rib-roughened rectangular duct was numerically simulated by using the large eddy simulation with a Lagrangian dynamic subgrid-scale model. The rotation number and the duct cross-sectional aspect ratio (0.25, 0.5, 1.0, 2.0, and 4.0) were varied for a friction Reynolds number of 350 and rib angle of 60degrees. The present results clearly showed the locally high heat transfer at several locations and how it was changed by the duct aspect ratio. The dissimilarity between the streamwise velocity and temperature was observed for all the aspect ratio cases in the rotating case. (C) 2003 Elsevier Science Ltd. All rights reserved.