In this paper, an experimental study of liquid/solid mass transfer at the wall of a trickle-bed reactor is presented. Three observed flow regimes were mainly analysed : trickling, pulsing and dispersed flows. The pressure drops in the trickling flow regime were interpreted by means of relative permeabilities approach. New mass transfer correlations are proposed in each of the flow regimes. A statistical analysis showed that all the parameters involved in these correlations were determined very accurately. The influence of Schmidt number was particularly investigated. It was found, through a qualitative analysis, that the experimental results were consistent with the theory of laminar boundary layer over a plane plate.