Three types of hydrophobic porous fillers (carbon blacks, in situ methylated silicas, and silylated silicas) were incorporated in PDMS (polydimethylsiloxane) membranes in order to find out under which conditions these filled membranes were advantageous for pervaporation of aqueous solutions, The properties of these fillers were changed systematically in order to maximize fluxes and selectivities in the pervaporation of aqueous ethanol, tertiary butyl alcohol, or aroma solutions. Ma-ny fillers were able to realize an increased membrane selectivity, but none of them could combine this with an increased organic flux. In ?his respect, silicas silylated with TMCS (trimethylchlorosilane) were found to be the best fillers. The filler addition was most beneficial when applying feed mixtures that induced low swelling in the membrane.