Measurements of two phase flow of water and steam in porous media were performed and relative permeabilities calculated. The goal was to compare the relative permeabilities from measurements using fluid of geothermal origin to known relative permeability curves, and to examine the effect of parameter variations. Due to high sensitivity to intrinsic (absolute) permeability, the data spread was large. Nevertheless, the Corey curves seem to be an appropriate curve for relative permeability functions. The results give insight into the behavior and characteristics of flashing of hydrothermal fluid in liquid dominated geothermal reservoirs. (C) 2014 Elsevier Ltd. All rights reserved.