High-pressure experiments on phase transitions of mantle-constituent minerals and bulk rocks provide indispensable data that clarify the mineralogical constitution of the deep mantle. This paper reviews the results of high-pressure experimental studies carried out in recent years. Phase relations of olivine-wadsleyite-ringwoodite transitions in pyrolite have been precisely determined to compare with seismological observations of the 410 and 520 km discontinuities. Results on the postspinel transition to perovskite + magnesiowüstite, which corresponds to the 660 km discontinuity, still have some controversies in transition pressure as well as the boundary slope. In pyrolite mantle, Ca-poor and Ca-rich pyroxenes are dissolved into garnet...