The gas sensing characteristics of porous BaTiO3-based ceramics, fabricated by adding graphite powders, were studied. All the sintered ceramics showed a tetragonal structure, irrespective of the added graphite content. The porosity of the BaTiO3-based ceramics increased with increasing graphite contents. It was found that the discrepancy in the resistivities measured at high temperatures (greater than or similar to200degreesC) in air and CO atmospheres became remarkable with temperatures. The sensitivity of CO gas was increased with porosity since the reactions between CO gas and O- and between CO gas and O are active at high porosity. The porous BaTiO3-based ceramics could be promising as a sensing material for CO gas sensor. (C) 2003 Elsevier B.V. All rights reserved.