Abstract Changes in the activity, selectivity and stability of fresh and industrially regenerated Pt Re/Al 2O 3-Cl catalysts with different numbers of operation cycles, due to changes in the chlorine content, were studied. Experiments under commercial operating conditions, including an accelerated deactivation period, were carried out in bench scale equipment. A typical naphtha cut from a commercial reforming unit was used as feed. Similar variations of activity and selectivity as a function of the chlorine content were found for all the catalysts studied. A minimum in coke formation per unit surface area at a concentration of 4.5 · 10 −5 g chlorine per m 2 was found. This is independent of the specific surface area or the number of industrial operation cycles. The phenomena are interpreted as a consequence of changes in the nature and distribution of the metal and acid active sites, produced by changes in the specific surface of the support due to the commercial operation.