The　aqueous　two-phase　system　formed　by　the　mixture　of　dodecyltrimethylammonium　bromide　(DTAB)　with　a　gemini　surfactant　O,O-bis(sodium　2-lauricate)-p-benzenediol　(C11pPHCNa)　has　been　studied.　Two　two-phase　regions　were　observed,　one　was　a　wide　region　in　the　cationic　surfactant-rich　side　and　the　other　in　the　vicinity　of　R　=　1:1,　where　R　is　the　mixing　mole　ratio　of　DTAB　to　C11pPHCNa　in　global　solution.　Multi-lamellar　vesicles　are　formed　in　the　concentrated　upper　phase　of　cationic　surfactant-rich　systems　and　spherical　aggregates　in　the　concentrated　bottom　phase　at　R　=　1:1.　The　microstructure　of　the　solution　and　the　phase　behavior　of　the　aqueous　two-phase　system　strongly　depended　on　the　total　concentration　and　the　composition　of　the　system.　©　2008　Elsevier　B.V.　All　rights　reserved.