The reforming of a paraffinic naphtha was studied in order to determine the influence of chlorination during the run. Experiments were performed at 505 degrees C, 15 kg cm(-2), WHSV = 4, H-2 : HC = 4, and with or without an 8 h initial period of deactivation at 1 kg cm(-2). A commercial Pt-Re/Al2O3 (0.3% Pt, 0.3% Re, 0.04% S, 0.15% Cl) catalyst was chlorinated using naphtha feeds with different H2O/Cl ratios. A model of the chlorination kinetics was developed and represents adequately the experimental results. The acid controlled reactions such as C-2-C-4 and production of C-5 paraffins, disappearance of C-9 paraffins and production of aromatics increase in parallel to the chlorination of the catalyst and the increase is independent of the amount of coke deposited on the catalyst. The sites of chlorine adsorption are different from the sites of coke deposition.