Applying accelerated techniques for catalyst synthesis and testing and a stochastic experimental design, two catalytic systems based on SO42-/ZrO2 and WOx/ZrO2 were seen as active and selective for n-paraffin isomerization. After three optimization cycles, a new catalyst formulation based on promoted SO42-/ZrO2 with improved activity and selectivity has been found. Characterization of the best catalysts generated in each cycle has been done. Activity and selectivity of the best catalyst found has been tested in the isomerization of a simulated industrial feed composed by n-pentane, n-hexane and n-heptane. For the second best catalytic system, i.e. WOx/ZrO2, the influence of tungsten content, promotor (Ce), nature of the starting precursor salt (sulfate, nitrate or chloride), and catalyst calcination temperature was studied using a factorial design. The relevance of the interaction between salt precursor and calcination temperature is discussed. (C) 2003 Elsevier B.V. All rights reserved.