The influence of up to 30 mol% zirconia doping on microstructure, liquid permeability, thermal and chemical stability of mesoporous composite titania/zirconia membranes was investigated. It was demonstrated that zirconia retards the phase transformation of anatase until at least 700 °C. The pore size decreased gradually to 3.6 nm by addition of up to 20 mol% zirconia, while nitrogen sorption experiments showed that the porosity, BET surface area and pore connectivity increased. Chemical stability tests showed that undoped titania and composite titania/zirconia materials were stable in the pH range 1–13 at room temperature. The mechanical strength of titania membranes was significantly improved by addition of zirconia. The permeability of titania and titania/zirconia composite membranes was eight times larger than that of γ-alumina. The permeability was not affected by the level of zirconia doping or by the nature of the permeating liquid.