Porous polymeric membranes made by polymerizing bicontinuous microemulsions stabilized with anionic sodium dodecyl sulfate (SDS) and cationic dodecyltrimethylammonium bromide (DTAB) as surface-active agents were investigated. The morphology, swelling and permeability characteristics of the membranes were found to be highly dependent on the surfactant concentration in both SDS and DTAB systems. The pore size of the DTAB system decreases on increasing the DTAB concentration, while the reverse trend was observed for the SDS system until its concentration exceeded 10 wt%. The membrane prepared using SDS was found to have a larger pore size in the range of 100 nm to 3 mu m as compared to that of DTAB, which is less than 100 nm. In addition, the variation of SDS concentration led 10 a continuous change in the shape of particle aggregates of the membranes while it appeared to remain in globular form for the DTAB system. The remarkable differences between the membranes prepared using SDS and DTAB are discussed in terms of their different monolayer flexibilities.