An experimental study is presented of a liquid-liquid dispersed/stratified flow in a horizontal pipe. The flow studied contains a highly concentrated layer of oil drops (light phase) under which flows a continuous layer of aqueous phase (heavy phase). The instant flow structure and hydrodynamics have been characterized in the aqueous phase using Particle Image Velocimetry in a matched refractive index medium. In this article, we focus on momentum transfer in the continuous aqueous layer at the wall, and at the interface, between the aqueous layer and the concentrated layer of oil drops. It is shown that, despite the presence of secondary flows, the velocity profile in the aqueous phase follows the classical logarithmic law near the wall. The shape of the tangential Reynolds stress profile in the aqueous layer is discussed in relation with the flow geometry and the presence of secondary flows. The mean interfacial shear stress is then derived from the macroscopic momentum balance applied in the aqueous layer cross-section. The local viscous stress contribution below the interface has been identified from the momentum balance equation in the vertical direction and an effective viscosity as a function of the local concentration has been derived. (C) 2007 American Institute of Chemical Engineers.