Highly monodispersed colloidal silica spheres in submicrometer sizes were synthesized by a chemical method.The sizes of silica spheres measured by transmission electron microscopy range from 200 to 600 nm in diameter, and its distribution standard deviation is less than 5%.Scanning Electron Microscopy images show that using selfcrystallization of the silica spheres, we have successfully obtained artificial opals with the three dimensional closepacked, facecentered cubic (fcc) silica matrixes. Reflection spectra study reveals that artificial opals show (111) directional photonic bandgap features.