Transition metal oxides make up a remarkable group of materials, exhibiting a wide variety of unusual electronic and magnetic properties. They have generated much interest, in particular since the discovery of high temperature superconductivity in the layered cuprates such as La2- xSrxCuO4. BiNiO3 is weakly antiferromagnetic at room temperature, and becomes a metal if it is pressurised. If the sample is cooled under pressure a new phase is seen which is poorly understood. The aim of this experiment is to verify the structure of this new phase, and its behaviour under pressure, and to determine if the sample retains its room temperature magnetic structure.