Composite chitin membranes supported by porous polyetherimide substrate were prepared fur the pervaporation separation of ethanol/toluene and mcthanol/toluene mixtures. The chitin was obtained by modifying chitosan to its original form chitin by the N-acetylation reaction. It was found that the incorporation of additional acetyl groups into the chitosan structure decreased the total flux and increased separation factor from 401 g/m(2) h; alpha=34 (pure chitosan) to 282 g/m(2) h; alpha=116 (4 mol acetylated chitosan) fur 10% EtOH feed mixture and from 681 g/m(2) h; alpha=159 (pure chitosan) to 484 g/m(2) h; alpha=607 for 10% MeOH feed mixture. It was concluded that chitin composite membranes could be a good candidate for this pervaporation system. Scanning electron microscopy and Fourier transform infrared determinations of the acetylated chitosan membranes were carried out and are reported. It was further shown that the chitin/polyetherimide composite membranes prepared had good pervaporation characteristics and were also found to be mechanically robust and stable to withstand the corrosive nature of the ethanol/toluene mixture during the pervaporation runs. This is the first reported successful application of chitin in the form of composite membranes for the pervaporation separation of organic/organic liquid systems.