Superior isomerization performance is obtained in an isomerization process employing a catalytic composition comprising a Group VIII noble metal and a hydrogen form mordenite incorporated with alumina. The superior isomerization performance is achieved using a catalyst composition having a surface area of at least 580 m.sup.2 /g. A novel method of preparing an isomerization catalyst having a surface area of at least 580 m.sup.2 /g is characterized by contacting a formed catalytic composite with an acidic aqueous solution prior to addition of the Group VIII noble metal. The isomerization process is particularly useful in the isomerization of a dimethylnaphthalene containing feedstock into a product that contains a higher concentration of the 2,6-dimethylnaphthalene isomer than did the feedstock.