The aim of the present study is to characterize wall shear stresses generated by a gas-liquid two-phase flow inside a capillary tube. In this case the flow is a slug flow. Two different approaches were used. The first one constituted a calculation of the shear stresses by a two-phase model in which some parameters characteristics of the flow were introduced. These parameters had been determined experimentally in a previous study. The second approach constituted a direct and local measurement of wall shear stresses by an electrochemical method. The shear stresses near liquid and gas slugs were obtained for different operating conditions. Moreover, a calculation of the liquid film thickness around the gas slugs demonstrated that this thickness does not depend on gas velocity. (c) 2005 American Institute of Chemical Engineers