An oriented submicron silicalite membrane has been prepared by growing a layer of oriented silicalite crystals on a composite precursor nanocrystalline silicalite/alumina film using controlled secondary growth. The orientation of the crystals at the surface was such that both straight and sinusoidal channel networks run nearly parallel to the membrane surface. The membrane exhibits ideal selectivities for H-2 over N-2 as high as 60 at 150 degrees C and O-2 over N-2 as high as 3.6 at 185 degrees C. H-2, N-2 and O-2 permeances are 2.13, 0.05 and 0.17 cm(3) (STP)/(cm(2) . min . atm) at 185 degrees C, respectively and the corresponding apparent activation energies are 11, 26 and 32 kJ/mol. The permeation characteristics are attributed to the preferred orientation of the molecular sieving layer.