The　interfacial　composition　of　the　stable　water/C12-s-C　12·2Br/n-hexanol/n-heptane　microemulsions　has　been　studied　in　detail　by　dilution　method.　The　results　showed　a　marked　maximum　amount　of　the　n-hexanol　populating　on　the　surfaces　of　droplets　(represented　as　a　=　n　ai/ns,　where　nai　and　ns　are　respectively　the　moles　of　n-hexanol　and　gemini　surfactant　on　the　surface　of　droplets)　with　increasing　water　content.　At　a　constant　level　of　water　addition　(the　molar　ratio　of　water　to　surfactant　W0　=　20),　a　decreased　with　increasing　the　spacer　length　in　the　C12-s-C　12·2Br　molecule.　The　structural　parameters　of　a　w/o　microemulsion　were　also　estimated　by　analyzing　the　data　of　dilution　experiments,　and　we　found　that　the　radius　of　the　water　pool　was　very　sensitive　to　the　increment　of　water　content.　The　radius　of　the　water　pool　varied　from　0.74　to　5.35　nm　with　increasing　W0　from　10　to　50.　The　variation　extent　reached　4.61　nm.　In　the　cases　of　water/CPC/n-butanol/isopropyl　myristate　and　water/CTAB/n-butanol/isopropyl　myristate,　however,　the　corresponding　variation　extents　were　only　1.22　and　1.68　nm,　respectively,　when　increasing　comparable　water　content.　The　ratio　of　N¯a/N¯2C,　where　N¯a　and　N¯2C　are　respectively　the　average　numbers　of　n-hexanol　and　the　total　average　numbers　of　alkyl　chains　of　gemini　surfactant　populating　on　per　droplet　surface,　decreased　obviously　with　increasing　water　content　at　W0　＞　15.　This　indicated　that　C　12-2-C12·2Br　favored　to　form　large　droplets　that　were　suitable　to　solubilize　more　water.　©　2006　American　Chemical　Society.