The pyrochlore-type Ca2Bi2O7 and Sr2Bi2O7 have been synthesized from a low-temperature hydrothermal route using NaBiO3.nH(2)O as a starting material. The crystal structures of these compounds were refined using synchrotron powder X-ray diffraction data. The cell parameters were found to be a = 10.75021 (5) angstrom and 10.94132 (6) angstrom for Ca2Bi2O7 and Sr2Bi2O7, respectively. Density functional theory calculations showed the metallic band structure, but the negligible mixing of O2 2p bands with the A-site alkaline-earth-metal states and weak overlap with the conduction bands result in the semiconducting behavior.