The invention concerns a process for preparing an oxide based on zirconium and titanium in which a liquid medium containing a zirconium compound and a titanium compound is formed; said medium is then heated; the precipitate obtained from the end of the preceding step is recovered and optionally, said precipitate is calcined. The invention also concerns an oxide based on zirconium and titanium. Said oxide can comprise in the range 30% to 40% by weight of titanium oxide and in this case it has a pure ZrTiO.sub.4 type structure or a mixture of phases of structure type ZrTiO.sub.4 and structure type anatase. Said oxide can also comprise in the range 10% to 20% by weight of titanium oxide and it then has a specific surface area of at least 40 m.sup.2/g after calcining for 5 hours at 800.degree. C.