SO4-ZrO2 catalysts, prepared by varying the conditions of oxide preparation and H2SO4 impregnation, have been characterized by means of different techniques (XRD, BET, Hammett-Bertolacini technique, XPS). The esterification of benzoic acid to methylbenzoate has been used to test the different catalysts and their catalytic performance has been discussed in the light of their bulk and surface properties.