8 mol% yttria-stabilized zirconia (8YSZ) ceramic is an oxide ion conductor at atmospheric pressure but shows the onset of p-type semiconduction, in addition to the preexisting oxide ion conduction, on application of a dc bias in the range 4-66 Vcm(-1 )and at temperatures in the range 150 degrees C-750 degrees C. The p-type behavior is attributed to the location and hopping of holes on oxygen. This contrasts with the commonly observed introduction of n-type conduction under reducing conditions and high fields. The hole conductivity increases with both dc bias and pO(2). Its occurrence may contribute to the early stages of flash phenomena in 8YSZ ceramics.