In the last 10 years extensive work was done in the preparation and characterization of molecular sieve membranes, especially of the types MFI, LTA and FAU. There is a remarkable progress in the synthesis of MFI membranes from the pure silica crystallization system. These silicalite-1 membranes show both separation properties by molecular size exclusion and by molecular interaction because of the hydrophobic interaction of the silica surface with permeating molecules. Silicalite-1 membranes exhibit promising permeation properties for industrially interesting mixtures as n-/iso-alkanes or the xylene isomers. However, so far these membranes are available only with areas of 1–10 cm 2, and the reproducibility of the membrane preparation is unsatisfactory. The yield of high-quality membranes is in the range of 10–30% of the preparations. In this work the membrane area was enlarged by the factor of 30, and the support shape was changed from a flat disc to a tube geometry. This was achieved by the optimization of the synthesis gel composition and the synthesis conditions. Furthermore, by changing the prepared membrane type from a mono- to a polylayer and by varying the calcination conditions, the density and size of leaks could be reduced. As a result of all these measures the yield of high-quality membranes with a minimum permselectivity of H 2 to SF 6 of 43 (which is five times the Knudsen factor) as a quality criterium was increased to 70% of all preparations. Special attention was given to the economy of the synthesis of MFI membranes which implies to save material, energy and time.