We observed the pressure-induced metal-insulator (MI) transition in BiNiO3 and studied the structural features under high pressure by means of synchrotron X-ray diffraction (SXRD). The results show that the transition from the triclinic insulating phase to the higher symmetric metallic phase with a hysteresis occurs in the vicinity of 3 GPa, which is associated with a melting of the oxygen holes trapped and ordered in the Bi-O sublattice. (C) 2004 Elsevier B.V. All rights reserved.