Nile　red　(phenoxazone-9)　was　used　as　a　fluorescence　probe　to　detect　the　sphere-to-rod-to-wormlike　micellar　transition　in　the　aqueous　mixtures　of　cetyltrimethylammonium　bromide　and　sodium　salicylate　or　potassium　bromide,　and　also　in　the　aqueous　solution　of　a　Gemini　surfactant,　ethanediyl-alpha,omega-bis(dimethyl　dodecyl　ammonium　bromide).　The　results　showed　the　l(a)/l(b)　of　Nile　red　(the　fluorescence　intensity　ratio　of　the　twisted　intramolecular　charge　transfer　band　to　the　planar　locally　excited　band)　was　a　more　sensitive　index　than　the　l(a)　(the　fluorescence　intensity　of　the　twisted　intramolecular　charge　transfer　band)　to　represent　the　micellar　transition.　This　was　attributed　to　the　special　molecular　structure　of　Nile　red　that　has　a　large　conjugated　ring　and　the　can　form　hydrogen　bond　with　water　molecules　at　the　electron　acceptor　group.　This　led　to　sensitive　response　of　the　twisted　intramolecular　charge　transfer　state　of　Nile　red　to　the　change　of　microenvironment.　(C)　2009　Elsevier　Ltd.　All　rights　reserved.