One of the basic impediments to a clear understanding of a variety of fundamental problems in the context of sediment transport has been the lack of a well-grounded formulation of bed sediment entrainment. This is dealt with herein, physically based on the mechanism that bed sediment particles are actually entrained by the bursting process inherent in wall turbulent flows. A simple theoretical model for sediment entrainment from flat, loose bed is established using the averaged bursting period scaled on inner variables and the spatialscales of turbulent bursts. Sediment entrainment is shown to depend strongly on bed-shear velocity. The theoretical entrainment flux is compared to available laboratory data sets covering both hydraulically smooth andtransitional bed situations. Generally good agreement is obtained, representing the best performance of the present model in relation to existing entrainment functions. It appears to characterize a rather encouraging aspect for a new approach to sediment transport, given the enhanced understanding of turbulent bursting.