Diffraction data from hexagonal boron nitride compiled through in situ synchrotron x-ray measurements under pressures and temperatures up to about 8 GPa and 1000 K, respectively, were analyzed in the light of Birch-Murnaghan's and Parsafar-Mason's equations of state. The isothermal bulk moduli at ambient conditions obtained from these equations almost coincide. However, the value, about 20 GPa, is appreciably small compared to the one reported previously. The x-ray diffraction patterns by which the current result is justified are presented. The possible origin of a large discrepancy in the values is discussed. (C) 2008 Elsevier Ltd. All rights reserved.