Nanometer-sized bismuth tungsten oxides, Bi2WO6s, were successfully synthesized by hydrothermal treatment at 200 ℃ for 24 hr, and their morphologies and crystallite sizes were influenced by adjusting the conditions to pH 4, 7, and 9. TEM images revealed that the particles were sheet-shaped and the crystallite sizes ranged from 7-120 nm. The samples absorbed in the visible range at about 380-400 nm. The lowest conductivity, 1.0×10^(6) ohm/square, was observed for Bi2WO6 prepared at pH 4 with a 150 nm film thickness. As the annealing temperature for Bi2WO6 prepared at pH 7 was increased, the conductivity decreased due of formation of larger particles by coagulation and sintering at high temperatures. Conductivity appears to improve with increasing film thickness up to 1,500 nm.