The activity and selectivity of rhenium promoted cobalt Fischer-Tropsch catalysts supported on Al2O3, TiO2 and SiO2 have been studied in a fixed-bed reactor at 483 K and 20 bar. Exposure of the catalysts to water added to the feed deactivates the Al2O3 supported catalyst, while the activity of the TiO2 and SiO2 supported catalysts increased. However, at high concentrations of water both the SiO2 and TiO2 supported catalyst deactivated. Common for all catalysis was an increase in C5+ selectivity and a decrease in the CH4 selectivity by increasing the water partial pressure. The catalysts have been characterized by scanning transmission electron microscope (STEM), BET, H-2 chemisorption and X-ray diffraction (XRD). (c) 2005 Elsevier B.V. All rights reserved.