Crystalline R-zirconium phosphate, Zr(HPO 4 ) 2 ‚H 2 O, was obtained by direct precipitation of soluble salts of zirconium(IV) with phosphoric acid. The fresh compound transforms, by hydrolysis, into amorphous or semicrystalline hydroxophosphates with a P/Zr molar ratio of less than two. These facts contradict the formation mechanism of zirconium phosphates admitted by researchers for over more than 40 years. The materials are characterized by chemical, textural, and thermal analysis, powder X-ray diffraction, and scanning electron microscopy.