Sulfated zirconia-titania and its transition metal doped compositions with 1.5 wt% iron, and 0.5 wt% manganese were prepared and characterized for surface acidity, and activity towards benzene alkylation. Acidity measurement of the 600degreesC calcined samples showed that upon doping with Mn, the protonic acid strength of the material increased, whereas iron doping decreased the strength of surface protons and followed the order Mn-SO42-/ZrO2-TiO2>SO42-/ZrO2-TiO2>Fe-SO42-/ZrO2-TiO2. Samples calcined at 110 and 600degreesC were XRD amorphous. However, on calcination at 800degreesC these samples showed crystalline phases characteristic of ZrTiO4. The Mn doped catalyst also showed highest activity and improved catalyst stability towards isopropylation of benzene. A good correlation between surface acidity and isopropylation activity was obtained. Increase in acidity in case of Mn doped sample was attributed to the increased stability of the surface sulfate groups.