The CaSiO3 perovskite has been synthesized in alaser-heated diamond-anvil cell at initial pressures rangingfrom 15 to 85 GPa. Chemical microanalyses of the quenchedproduct show negligible solubility in the CaSiO3 perovskite ofaluminum from the ruby added for pressure measurements.The compression of CaSiO3 perovskite has been measured to96 GPa with X-ray methods. The results do not show asignificant deviation of Ko' from 4, and with a Birch-Murnaghan equation of state we obtain a 1-bar molar volumeVo = 45.60 ¿ 0.10 ¿3 and a bulk modulus Ko = 275 ¿ 15GPa. This perovskite may be an invisible component of thelower mantle in view of the similarity of its density with thatgiven by the standard Earth model. PREM.