Polysulfone　(PSf)　flat-sheet　membranes　with　bi-continuous　porous　surfaces　for　direct-contact　membrane　distillation　(DCMD)　were　successfully　fabricated　using　a　vapor-induced　phase　separation　(VIPS)　method.　The　present　investigation　revealed　how　the　surface　and　cross-sectional　morphology　of　PSf　membranes　and　the　desalination　performance　in　DCMD　were　affected　by　exposure　time,　PSf　content　and　relative　humidity　of　air.　In　the　VIPS　process,　an　increase　in　exposure　time　led　to　a　replacement　of　the　bi-continuous　top　surface　with　a　dense　skin　and　to　a　large　decrease　in　the　permeate　flux　in　DCMD.　The　best　PSf　membrane　fabricated　in　this　study　had　a　mean　pore　radius　of　0.32　mu　m,　water　contact　angle　of　106.4　degrees,　the　liquid　entry　pressure　of　water　of　300　kPa,　and　total　porosity　of　82.1%.　During　the　DCMD　process　with　a　35　g/L　sodium　chloride　solution,　the　best　membrane　produced　a　permeate　flux　of　30.0　kg　m(-2)　h(-1)　and　a　very　low　conductivity　of　distilled　water　at　hot-feed　and　cold-distillate　side　temperatures　of　73　degrees　C　and　25　degrees　C,　respectively.　The　thickness　of　the　hydrophobic　layer　of　the　membranes　was　first　measured　using　the　weight　method,　and　its　value　was　used　in　a　simulation　of　the　DCMD　process.　(C)　2013　Elsevier　B.V.　All　rights　reserved.