Isomerization of n-heptane over Ni-WOx/Al2O3-SiO2 catalysts was carried out in a continuous flow fixed-bed reactor under atmospheric pressure. The first part of this study deals with the preparation of two series of catalysts (A and B) by the sol-gel method, while the second part deals with the isomerization of n-heptane. The principal objective of this study was to choose the catalyst giving the best isomer yield (di- and tri-branched ones) with optimum reaction conditions ( reaction temperature, reduction temperature and time on stream). From the results obtained, the optimum nickel content was found to be 15 wt% and it seems that the incorporation of tungsten ( B series) leads to a significant enhancement in the activity of the prepared catalysts. After running on stream for 100 min, the catalyst with 15% nickel and 10% tungsten ( B4 catalyst) gives the best results (29% conversion and 70% selectivity) at 250 degreesC.