The flow of two immiscible liquids in a horizontal pipe with an inner diameter of 59 mm and a total length of 48 m is experimentally investigated. Results are presented for the effect of emulsification and phase inversion on the pressure drop for different flow regimes of two phase oil-water mixtures. The measurements are conducted for oil viscosities of 22, 27 and 35 mPas, which are obtained by changing the temperature of the liquids. For the how conditions investigated maximum pressure drops are measured in the region of phase inversion which is observed for input water fractions between 10 and 20%. There is no significant effect of the temperature on the dow characteristics observed.