The production of C-4-C-6 branched isoalkanes by isomerization-cracking of n-octane (300 degrees C, 0.1 MPa) using sulfated zirconia catalysts was studied. The effect of Ni addition on the activity and selectivity was compared to the effect of Pt. Pt enhanced the activity and stability of the catalysts. Ni mainly improved the selectivity to isoparaffins (maximum yield at 1% Ni). n-Octane conversion fully correlated with total acidity. Average and final stable conversion values were in comparison lower for Ni catalysts. This result was addressed to the lower metal activity of Ni and to the detrimental effect of sulfated zirconia on the reducibility of the metal.