An　experimental　study　on　the　structural　behaviour　of　concrete-filled　stiffened　thin-walled　steel　tubular　columns　is　presented　in　this　paper.　The　stiffening　was　achieved　by　welding　longitudinal　stiffeners　on　the　inner　surfaces　of　the　steel　tubes.　Companion　tests　were　also　undertaken　on　12　unstiffened　concrete-filled　steel　tubular　(CFST)　columns,　with　or　without　steel　fibres　in　the　infill　concrete.　The　test　results　showed　that　the　local　buckling　of　the　tubes　was　effectively　delayed　by　the　stiffeners.　The　plate　buckling　initially　occurred　when　the　maximum　load　had　almost　reached　for　stiffened　specimens,　thus　they　had　higher　serviceability　benefits　compared　to　those　of　unstiffened　ones.　Some　of　the　existing　design　codes　were　used　to　predict　the　load-carrying　capacities　of　the　tested　composite　columns.　©　2007　Elsevier　Ltd.　All　rights　reserved.