In order to examine pressure-volume-temperature (P-V-T) relations for CaSiO3 perovskite (Ca-perovskite), high-temperature compression experiments with in situ X-ray diffraction were performed in a laser-heated diamond anvil cell (DAC) to 127 GPa and 2,300 K. We also employed an external heating system in the DAC in order to obtain P-V data at a moderate temperature of 700 K up to 113 GPa, which is the reference temperature for constructing an equation of state. The P-V data at 700 K were fitted to the second-order Birch-Murnaghan equation of state, yielding K 700,1bar = 207 ± 4 GPa and V 700,1bar = 46. 5 ± 0. 1 Å. Thermal pressure terms were evaluated in the framework of the Mie-Grüneisen-Debye model, yielding γ 700,1bar = 2. 7 ± 0. 3, q 700,1bar = 1. 2 ± 0. 8, and θ 700,1bar = 1,300 ± 500 K. A thermodynamic thermal pressure model was also employed, yielding α 700,1bar = 5. 7 ± 0. 5 × 10−5/K and (∂K/∂T) = -0. 010 ± 0. 004 GPa/K. Computed densities along a lower mantle geotherm demonstrate that Ca-perovskite is denser than the surrounding lower mantle, suggesting that Ca-perovskite-rich rocks do not rise up through the lower mantle. One of such rocks might be a residue of partial melting of subducted mid-oceanic ridge basalt (MORB) at the base of the mantle. Since the partial melt is FeO-rich and therefore denser than the mantle, all the components of subducted MORB may not return to shallow levels.