The effect of adsorbed surfactants on the flow that takes place in the film forming zone of the slot coater is examined. The numerical technique employed in this work, that is based on the finite element method, can suitably handle viscous free surfaces with locally varying interfacial properties. The complete information produced by the computational code allows to relate the interfacial dynamics to the mechanism involved in the mass transport process: convection and adsorption/desorption. The results presented show that the effect produced by both interfacial viscosity and interfacial elasticity are rather similar; however, the operating conditions that make them more noticeable are different. ©1996 American Institute of Physics.