The positive temperature coefficient of resistivity (PTCR) characteristics of donor-doped BaTiO3 fired in a reducing atmosphere and reoxidized in air are investigated. The result reveals that conventional semiconducting BaTiO3 ceramics fired in a reducing atmosphere and reoxidized at a low temperature of 800 degrees C in air show minimal PTCR characteristics, as reported earlier; however, Ca-doped BaTiO3 with compositions in the range of 1.005 <=(Ba+Ca+La)/Ti <= 1.010 exhibit pronounced PTCR characteristics, even when reoxidized at such a low temperature. The semiconducting BaTiO3 ceramics with {(Ba+Ca+La)/Ti} = 1.005 and Ca-doped to 20 mol% exhibit remarkable PTCR characteristics with a resistivity jump of two orders of magnitude when they have been reoxidized at 800 degrees C after firing in a reducing atmosphere.