We have re-examined the crystal structure and equation of state of MgSiO3 perovskite by single-crystal X-ray diffraction up to 10 GPa. We have determined an isothermal bulk modulus K0 = 253(1) GPa with K'0 = 4, which is in excellent agreement with the adiabatic bulk moduli reported in recent studies by Brillouin spectroscopy and ultrasonic interferometry. We confirm that the compressibility of perovskite is anisotropic with the b-axis being the least compressible direction. On compression, the bond lengths and angles on Mg-site and Si-site decrease continuously, indicating that the structure gets more distorted as pressure increases. This is supported by a general model for perovskites that predicts that the octahedra become more tilted at lower mantle pressures.