Monomethylhydrazine (MMH) is a well-known liquid propellant used as fuel for launching of rockets and satellites. The desalted reaction liquor of MMH contains about 2 wt % of the propellant (balance water), which also forms an azeotrope with water at 35% MMH concentration. Removal of water to obtain pure MMH by conventional separation methods such as distillation is hazard prone and expensive. The potential of the membrane-based pervaporation technique has been investigated in this study for enriching aqueous solutions of MMK. Ethylcellulose membrane, which is selected on the basis of estimations of Flory-Huggins interaction parameters and Hansen's solubility parameter, gives promising results and is resistant to chemical attack by MMH. The effect of operating parameters such as feed concentration and membrane thickness on flux and selectivity are evaluated. Finally aging studies have been carried out to determine the life of the membrane in the propellant medium.