A model that attributes the aeration of the liquid slug to a recurrent bubble entrainment from the Taylor bubble (TB) tail is introduced. The bubble fragmentation is related to the rate of turbulent kinetic energy produced in the wall jet and shear layer, which are formed in the TB wake as the liquid film plunges into the slug front. The bubble fragmentation model has been incorporated into a complete model, which suggests a unified method for the prediction of the slug void fraction and other slug characteristics in horizontal, inclined and vertical slug flow. The model has been tested against experimental data available from the literature and was found to predict the effects of liquid and gas flow rates and their physical properties, as well as tube diameter and inclination. (C) 2004 Elsevier Ltd. All rights reserved.