Abstract: There is provided a catalytic composition which comprises a mixture of a crystalline chromosilicate and an oxide of chromium, said catalytic composition providing a specific X-ray diffraction pattern and having the following composition in terms of mole ratios of oxides:0.9.+-.0.2 M.sub.2/n O:Cr.sub.2 O.sub.3 :YSiO.sub.2 :ZH.sub.2 O,wherein M is at least one cation having a valence of n, Y is a value within the range of about 4 to about 500, and Z is a value within the range of about 0 to about 160. There is also provided a method for preparing such a catalytic composition.There is provided a process for the conversion of a hydrocarbon stream which comprises contacting said stream at conversion conditions with the above catalytic composition. In addition, there is provided a process for the isomerization of a xylene feed which comprises contacting said feed at isomerization conditions with the above catalytic composition.