The study of combined heat transfer of convection and radiation in rectangular ducts rotating in a parallel mode was investigated numerically in detail. The coupled momentum and energy equations are solved by the DuFort-Frankel numerical scheme to examine the interactions of convection with radiation. The integro-differential radiative transfer equation is solved by the discrete ordinates method. Results are presented over a wide range of the governing parameters. The present results reveal that the rotational effect in a square duct is more significant than that in a rectangular one. The predictions also demonstrate that the radiation presents significant effects on the axial distributions of the total Nusselt number, Nu, and tends to reduce the centrifugal-buoyancy effects. The effect of rotation on the Nu(t), is restricted in the entrance region, however, the radiation affects the heat transfer through out the channel. Additionally, the Nu(t), increases with the decrease in the conduction-to-radiation parameter N-C. (c) 2007 Elsevier Ltd. All rights reserved.