Nano-polycrystalline diamond cubes with an edge length of 6mm have been used as anvils for Kawai-type multianvil apparatus. The maximum pressure of ∼88GPa was confirmed based on in situ X-ray diffraction measurements using nano-polycrystalline diamond anvils with a truncation of 1.0mm, which is more than 50% higher than the pressure (∼56GPa) achieved at the same press load using sintered-diamond anvils. The X-ray transparency of the nano-polycrystalline diamond anvil was found to be about 10–100 times as high as that of sintered-diamond anvils for a wide range of photon energies (∼30–130keV), leading to high-quality X-ray imaging and diffraction profiles of the sample under pressure, even through the anvils. It is expected that further optimization of the pressure medium and gasket would lead to pressures far higher than 100GPa without sacrificing the advantages of the multianvil apparatus over diamond anvil cells.