Purpose - The purpose of this paper is to study a multiphase-flow instrumentation for film thickness measurement, especially impedance-based, not only for gas-liquid flow but also for mixtures of immiscible and more viscous substances such as oil and water. Conductance and capacitive planar sensors were compared to select the most suitable option for oil - water dispersed flow. Design/methodology/approach - A study of techniques for measurement of film thickness in oil - water pipe flow is presented. In the first part, some measurement techniques used for the investigation of multiphase flows are described, with their advantages and disadvantages. Next, examinations of conductive and capacitive techniques with planar sensors are presented. Findings - Film thickness measurement techniques for oil-water flow are scanty in the literature. Some techniques have been used in studies of annular flow (gas-liquid and liquid-liquid flows), but applications in other flow patterns were not encountered. The methods based on conductive or capacitive measurements and planar sensor are promising solutions for measuring time-averaged film thicknesses in oil-water flows. A capacitive system may be more appropriate for oil-water flows. Originality/value - This paper provides a review of film thickness measurements in pipes. There are many reviews on gas - liquid flow measurement but not many about liquid - liquid flow.352 200209