A physical model is developed to predict the hydrodynamic parameters of steady-state cocurrent gas-liquid flow through trickle-bed reactors operating in the trickle flow regime. The trickle flow is described by an annular pattern in which the gas and liquid phases are completely separated by a smooth and stable interface. The formulation of the model involves balance equations deduced from the macroscopic mass and momentum conservation laws. The particle-liquid drag and the gas-liquid interactions, i.e. the gas-liquid drag due to the relative motion between the fluids and the force by which the gas pushes the liquid against the solid particles, are evaluated from theoretical considerations. The predictions of the liquid saturation and pressure gradient from the model are found to be in good agreement with existing experimental data obtained in a wide range of operating pressure (0.1-10 MPa) for various gas-liquid and packing systems. The present model predicts these two hydrodynamic parameters with a better accuracy than the available correlation ones. Some underestimation of the pressure gradient is observed for the highest values of the superficial gas velocity and operating pressure due to the droplets entrainment and the wavy pattern of the gas-liquid interface that are not taken into account. The fundamental feature of the present model is the total absence of adjustable constants.