Interpenetrating polymer network(IPN) membranes of polyurethane (PU) and polymethylmethacrylate (PMMA) cross linked with ethylene glycol dimethacrylate (EGDMA) were prepared and characterized with respect to swelling behavior and pervaporation for the benzene/cyclohexane mixtures through these membranes. In the result of tensile test, the membrane cross-linked with 10 wt% EGDMA showed the maximum tensile strength. The density was decreased when the content of EGDMA was more than 10 wt%. The electrical properties of the IPN membranes were also investigated by DEA. The PU/PMMA IPN membranes showed two broad glass transitions where the T_g values approached each other with increasing EGDMA contents. All of the membranes exibited high selectivities of benzene in the benzene/cyclohexane mixtures and the permeabilities of benzene increased with the concentration of benzene in the feed solutions. The swelling behaviors of membranes were depressed with the increasing contents of the crosslinking agent. This result in benzene/cyclohexane mixture leads to the increase of the selectivity for benzene. In particular, the membrane cross-linked with 15 wt% EGDMA showed excellent benzene selectivities in low concentration of benzene.