Effects of oxygen partial pressure (P-O2) control on the electrical properties and microstructural development of (Ba1-xHox)(0.997)TiO3 were studied. An oxidation condition (P-O2 similar to 1.0 atm) was maintained during the heating process, and then the specimen was sintered in a reducing atmosphere (P-O2 < 10(-9) atm) at 1350 degrees C, followed by the annealing process at 1000 degrees C and P-O2 = 1 atm. The switching temperature (T-S) from the oxidation atmosphere to the reducing condition was changed from 1100 to 1350 degrees C. A significant decrease in the room-temperature resisitivity (rho(25)) was observed as T-S was increased. The temperature coefficient of resistance (TCR) was independent of the change in T-S, and closed pores decreased with increasing T-S.