Here we report the phase boundaries between majorite, akimotoite (ilmenite), and perovskite in MgSiO3 determined by in situ measurements in a multi-anvil apparatus. We used both gold and platinum as internal pressure standards at high pressure and temperature. Our results obtained at 1400--2000¿C, together with previous results obtained at 1000--1200¿C by Ono et al. [2001>, precisely locate the akimotoite-perovskite transition boundary at P (GPa) = 25.09 - 0.0027 ¿ T (¿C), based on the P-V-T equation of state of gold [Anderson et al., 1989>. Our new experimental data show the position of triple point to be 20.0 GPa and 1920¿C. The present measurements reconfirm our earlier study [Hirose et al., 2001> that Anderson's gold pressure scale gives slightly higher pressures than the platinum pressure scale proposed either by Jamieson et al. [1982> or Holmes et al. [1989>. ¿ 2001 American Geophysical Union