Barium zirconium diorthophosphate BaZr(PO4)(2) was synthesised and its high temperature behavior was studied. At room temperature the compound was found to have a monoclinic structure, in agreement with earlier literature reports. A monoclinic-to-hexagonal phase transition at about 733 K was found by differential thermal analysis; this transition was confirmed by X-ray diffraction and drop calorimetry. (c) 2005 Elsevier B.V. All rights reserved.