Separation of methanol (MeOH) and isopentane (iC(5)) is a problematic process in the production of tertiary-amyle methyl ether (TAME). The removal of methanol from the product stream and its subsequent recycling to the reactor requires breakage of its azeotrope with iC5. While the conventional separation processes are costly and cumbersome, pervaporation offers a simple and inexpensive alternative to traditional techniques. In the present study, pervaporation was used to examine the performance of two commercial rubbery membranes as well as Nafion-170 to separate methanol and isopentane. The results indicate that all three membranes were highly selective and permeable toward methanol. Both the selectivity and permeability were strongly feed-composition dependent. Selectivity decreased and permeability increased as methanol concentration in the feed increased. With few exceptions, methanol was collected at 95% to 99.8% purity from the permeate side at a wide range of feed compositions varying from 1% to 25% methanol. Average selectivities of 170 to 370, and fluxes up to 2.93 kg/m(2).h were observed. We also found that preconditioning of the membranes enhances their performances.