In situ high-pressure (up to 44-53 GPa) energy dispersive x-ray diffraction experiments have been carried out on CaTiO CaTiO 3, structure, high pressure, equation of state in a diamond anvil cell at room temperature by using synchrotron radiation. Experimental data show that the a and b axes have similar compressibilities with large variation, while the c axis is less compressible with increasing pressure. However, there is no evidence of any structural transformation in this pressure range. The isothermal P-V equation of the state of CaTiO CaTiO 3, structure, high pressure, equation of state is fitted using the Murnaghan equation of state, which yields values of V0=0.2245(6)nm 3 and K 0=222(9) GPa assuming the pressure derivative K′0=4 According to the relation of the pseudo-cubic angle γpc and pressure, the structure of CaTiO CaTiO 3, structure, high pressure, equation of state will reduce its symmetry under hydrostatic pressure.