Preparation of the silicalite membrane with a seed technique on the porous sintered stainless steel support disk with an average pore diameter of 2 mum was examined under various hydrothermal synthesis conditions. Effects of the chemical composition of the starting hydrogel and the seed crystal size on the silicalite membrane formation were studied systematically. The reproducibility of the seed technique was high as compared with a conventional method without seeds. The silicalite membrane was obtained when the TPABr concentration in the hydrogel was very low (0.003 less than or equal to TPABr/SiO(2)less than or equal to0.005). It was also found that the pervaporation performance of the silicalite membrane obtained was greatly dependent on the crystal size of the silicalite seed. The highest separation factor was obtained when seed crystals with 12 mum in size were used.