The kinetics of the Fisher-Tropsch synthesis is studied in a laboratory CSTR slurry reactor using a commercial Cobalt catalyst. The rates of CO consumption and of production of hydrocarbons are modeled using a mechanism that accounts for olefin readsorption. The rate expressions are expressed in terms of liquid phase concentrations. The rate parameters are determined from experiments performed at 220 degrees C, 2 MPa and H-2/CO feed ratios of 1.6-3.35. The model gives a good prediction of the paraffin distribution. The effect of olefin readsorption (deviation to ASF distribution) seems minor and the corresponding rate parameters are poorly determined. The effect of water concentration remains to be more deeply investigated. (c) 2007 Elsevier Ltd. All rights reserved.