Several novel crystalline layered zirconium phosphates with composition Zr2O3(HPO4)-nH2O (M=Na, K) were prepared by the partial hydrolytic decomposition of amorphous or crystalline a-zirconium phosphates in alkaline media under mild hydrothermal conditions. The corresponding Li-and Cs-forms of this phosphate were obtained by successive treatment of Na- or K-forms with LiOH or CsOH solutions. Two hydrogen forms of the novel zirconium phosphate (Ψ-ZrP) - Zr2O3(HPO4)-1.5H2O and Zr2O3(HPO4)-0.5H2O were prepared by acid treatment of the salt forms. The intercalation of n-alkylamines into the Ψ-ZrP-H from the gas phase was also studied. All the synthesized materials were characterized by elemental analysis, TGA, X-ray, IR and31P MAS NMR spectroscopy. The data indicate that the novel zirconium phosphate is a monohydrogen phosphate. It was found also that Ψ-ZrP exhibits unexpectedly and extremely high hydrolytic stability in alkaline media; the phosphorus release in 1M NaOH being lower than 0.11 -0.13 mmol PO4/g in comparison with the complete hydrolytic decomposition of other known layered zirconium phosphates in this medium. The ion exchange behavior of the novel Ψ-zirconium phosphate in its H-form, theoretical ion exchange capacity (IEC) of 2.86 meq/g, as well as Na- and K-forms towards alkali, alkaline-earth, and some di- and tri-valent metal cations in different model solutions was studied over a wide pH range (2-14) by the batch technique and an explanation of the experimental facts is proposed.