This work reports the pervaporative separation of ethanol from ethanol-ethyl ter butyl ether mixtures using a commercial membrane, PERVAP 2256, that previously showed an interesting behavior in the separation of methanol-MTBE mixtures. Pervaporation flux has been obtained and analyzed as a function of feed composition in the range of ethanol concentration of 30-50 wt % and temperature in the range of 50-70degreesC whereas permeate pressure was kept constant in all the experiments and equal to 3 mmHg. Pervaporation fluxes showed an exponential dependence with both variables, that in the case of temperature fitted to an Arrhenius type expression. Achievement of steady state conditions referred to the pervaporation flux needed of long times that depended on the previous history of the membrane; thus new membranes needed a long conditioning period before reaching steady state that was considerably shortened in subsequent changes of the operation conditions.