Ceramic ZrO2 and TiO2 nanofiltration membranes were produced by using a polymeric sol gel route. The influence of different parameters like additives and solvents onto the hydrolysis and polycondensation properties of the sols was studied by IR- and NMR-spectroscopy and viscosity measurements. The prepared ceramic membranes were characterized by different methods. Structure and phases were investigated by X-ray diffraction, thickness and qualify by the aid of SEM and FESEM. The membranes exhibit an average pore size in the range of 1-2 nn as determined from N-2-adsorprion-desorption measurements. The filtration properties of the membranes were examined by filtration tests with two colouring agents. A cut-off value of less than 1000 Da was determined.