X-ray powder diffraction data for the high temperature phase of NaBi3V2O10obtained fromin situ high temperature XRD studies are presented. NaBi3V2O10 undergoes a phase transition from triclinic to monoclinic at about 600 °C. The unit cell parameters of the high temperature monoclinic phase at 600 °C area:= 12.3899(21), b=5.5642(10), c=7.1543(18) Å and β= 98.393(16)°,V= 487.94(13)Å3 and Z=2, þcal = 6.20 g / cc. On further increasing the temperature, it partially decomposes to a γ-Bi4V2O11 type phase. The details of this phase as well as the stability of NaBi3V2O10 are discussed