A procedure has been developed to prepare ultra-thin zeolite films supported on Si(100). Films were prepared by spin-coating a solution of Silicalite-1 zeolite precursors diluted in ethanol, followed by hydration in water vapour and heating to 60 C. High resolution transmission electron microscopy analysis of sample cross-sections shows that the surfaces are both smooth and continuous, and films of approximately 2 and 15 nm thickness were prepared by varying the precursor dilution factor. Electron diffraction analysis shows that the 15 nm film is an amorphous arrangement of Silicalite-1 precursors. Atomic force microscopy measurements confirm that the surface is smooth over a range of several microns. (C) 2003 Elsevier B.V. All rights reserved.