A modified McQuiston model for evaluating the wet fin efficiency of cooling and dehumidification coils has been developed by modifying the existing popular McQuiston model and is reported in this paper. The condensate film moving on fin surfaces and its impacts on heat transfer have been taken into account in deriving the governing equation for fin temperature, and consequently, the enthalpy change of the moving condensate film has been included in the governing equation for fin temperature. The modified McQuiston model was validated by comparing its predictions with those using the McQuiston model under the same operating and boundary conditions. It is expected that the modified McQuiston model developed can be applied not only to the commonly seen air cooling and dehumidification but also to certain special operations such as industrial steam condensation. (C) 2008 Elsevier Ltd. All rights reserved.