Silica-based　membranes　prepared　by　chemical　vapor　deposition　of　tetraethylorthosilicate　(TEOS)　on　gamma-alumina　overlayers　are　known　to　be　effective　for　hydrogen　separation　and　are　attractive　for　membrane　reactor　applications　for　hydrogen-producing　reactions.　In　this　study,　the　synthesis　of　the　membranes　was　improved　by　simplifying　the　deposition　of　the　intermediate　gamma-alumina　layers　and　by　using　the　precursor,　dimethyldimethoxysilane　(DMDMOS).　In　the　placement　of　the　gamma-alumina　layers,　earlier　work　in　our　laboratory　employed　four　to　five　dipping-calcining　cycles　of　boehmite　sol　precursors　to　produce　high　H-2　selectivities,　but　this　took　considerable　time.　In　the　present　study,　only　two　cycles　were　needed,　even　for　a　macro-porous　support,　through　the　use　of　finer　boehmite　precursor　particle　sizes.　Using　the　simplified　fabrication　process,　silica-alumina　composite　membranes　with　H-2　permeance　＞　10(-7)　mol　m(-2)　s(-1)　Pa-1　and　H-2/N-2　selectivity　＞100　were　successfully　synthesized.　In　addition,　the　use　of　the　silica　precursor,　DMDMOS,　further　improved　the　H-2　permeance　without　compromising　the　H-2/N-2　selectivity.　Pure　DMDMOS　membranes　proved　to　be　unstable　against　hydrothermal　conditions,　but　the　addition　of　aluminum　tri-sec-butoxide　(ATSB)　improved　the　stability　just　like　for　conventional　TEOS　membranes.