Abstract: Bridged/lamellar metallic oxides, e.g., those of vanadium, molybdenum, tungsten and titanium, which have large and stable specific surfaces and are well adopted as catalysts, are prepared by (a) intimately admixing a gel of a metallic oxide having a lamellar structure with a cationic solution, (b) adding a solution of a spheroidal cationic species, e.g., a polyoxocation of aluminum, chromium, zirconium, nickel, molybdenum, niobium or tantalum, to the reaction medium thus produced, and then (c) aging the reaction medium for such period of time as to exchange the spheroidal cationic species for the cations introduced in step (a).