Na2ZnP2O7.HCl single crystals were synthesised by hydrothermal technique and characterised by X-ray diffraction method. The compound crystallises in tetragonal system with space group P4(1)2(1)2 and cell parameters a = 7.687(5) Angstrom, c = 20.529(1) Angstrom, Z = 8, having tunnel type of cavities in the structure. DTA study indicates that this compound is thermally fairly stable. (C) 2003 Elsevier Ltd. All rights reserved.