Communication: Silica membranes exhibiting excellent molecular sieving capability which would find applications in fuel-cell electric vehicles with on-board hydrogen generation, for example, are the aim of the sol-gel strategies outlined here. It is shown that optimization of the sol-gel synthesis parameters is important in order to achieve membranes with minimum defects and hence high selectivity. The preparation of the supported membranes is described and the gas permeation behavior of membranes made from different sol compositions reported.