Porous TiO2 ceramics were prepared by adding various amounts of Li2O and V2O5 and the humidity sensitivity of the resulting ceramics was investigated by means of electrical measurements, scanning electron microscopy and mercury intrusion porosimetry. Simultaneous addition of Li2O and V2O5 to TiO2 enabled sintering at temperatures as low as 700 degrees C and also decreased the impedance of the ceramics. Furthermore, in the ceramics including these additives simultaneously, excellent humidity sensitivity as well as good response characteristics were observed. The microstructures of these ceramics depended on the firing temperature and the amount and ratio of Li2O/V2O5, and optimum humidity sensitivity was observed for the sample including both 0.25 mol% Li2O and 0.75 mol% V2O5 fired at 700 degrees C. These results indicated that the humidity sensitivity and its response characteristics were closely related to the microstructure, and that improving the uniformity of microstructure is important for improving humidity sensitivity and its response characteristics. (C) 2007 Elsevier Ltd and Techna Group S.r.l. All rights reserved.