Inorganic nanofiltration membranes were fabricated from silica-zirconia composite colloidal sol (molar ratio Si/Zr=9/1) using a sol-gel process. Molecular weight cut-off (MWCO) was successfully controlled between 200 and 1000 Da by regulating the colloidal diameters of sol solutions in the final coating stage. The pure water permeabilities ranged from 0.15 x 10(-11) to 1.5 x 10(-11) m(3) m(-2) s(-1) Pa-1. Pore size and pore size distribution were estimated based on the dynamic method of humid air permeation, and found to be from 1.0 to 2.9 nm. The MWCO obtained from NF experiments using neutral organic solutes corresponds well with the pore diameters estimated from the dynamic permeation method. Silica-zirconia membranes were found to be stable in aqueous solution for periods in excess of four months.