A counter-diffusion chemical vapor deposition method using siloxanes (hexamethyldisiloxane (HMDS), 1,3-divinyltetramethyldisiloxane (DVTMDS), 1,3-dioctyltetramethyldisiloxane (DOTMDS)) as silica precursors was employed to prepare composite silica membranes, showing stable hydrogen permselectivity at high temperature. The membrane prepared with HMDS showed a H(2) permeance of 1.2 X 10(-6) mol . m(-2) . s(-1) . Pa(-1) and a H(2)/N(2) ideal selectivity of 550 at 873 K, and 1.0 X 10(-6) mol . m(-2) . s(-1) . Pa(-1) and 590 at 1073 K. The H(2) permeance was about one order of magnitude larger than that of the conventional silica membrane prepared with tetramethylorthosilicate (TMOS) as a silica precursor. It was found that the H, permeance of the HMDS silica membrane initially decreased about 8% and was then maintained for 200 h at 773 K, whereas that of the TMOS silica membrane decreased gradually. Hydrothermal stability test was also carried out in a stream of nitrogen including steam at 773 K. Though an initial 26% drop in the H(2), permeance was observed, the change afterwards was small during a 20-h test. It was shown that the use of a precursor having the siloxane structure was effective in preparing silica membranes with high temperature durability.