gamma alumina microporous membranes, produced from a sol-gel process, were grafted by means of chloro-, methoxy- or ethoxy-organosilanes. The grafting conditions were first tested on gamma alumina powders which were characterised by means of thermogravimetric analysis and nitrogen adsorption. The membrane material was studied by means of infrared spectrometry, nitrogen adsorption and nitrogen permeation. The performances of grafted and ungrafted membranes were examined for the separation by pervaporation of binary mixtures such as water/ethanol, cyclohexane/toluene, ethanol/cyclohexane and methylethylketone/cyclohexane.