Microporous TiO2 membranes were developed by a polymeric sol-gel technique on top of a specially designed tubular ceramic multi-layer support. The microporosity of the membrane is 28% and depends strongly on the amorphous state of the TiO2. N-2-sorption measurements indicated cylindrical pores with a mean diameter of 0.9 nm which was confirmed by filtration tests using molecular weight standards. The membrane has a cut off of 480 Da and a pure water flux of 20 l/(m(2) h bar). Salt retention depends on the pH and the salt concentration. At a pH above 5.8, the retention of sulphate ions is more than 90%.