Isomerization of xylenes in admixture with ethyl benzene by contact with a zeolite catalyst such as ZSM-5 is improved by use of zeolite having a substantial alkali metal content at a temperature above about 800.degree. F. At these conditions, conversion of ethylbenzene follows a different reaction path which permits high conversion of ethylbenzene to benzene without loss of xylenes by disproportionation.