Sulfated titanium-modified pillared montmorillonites using (NH4)(2)SO4 and H2SO4 have been prepared. The influence of the method of sulfation and of the SO42-/Ti mole ratio was studied. An important effect in both the basal spacings and the acidic properties was observed when (NH4)(2)SO4 or H2SO4 is present in the solution of intercalation. When titanium pillared clays (Ti-PILCs) are sulfated by impregnation, their acidity initially increases, irrespective of the sulfate source, whereas their basal spacings are not modified. A loss of specific surface area is observed when the temperature of calcination or the SO42-/Ti mole ratio is increased.