Tests　are　reported　on　twenty-six　concrete　filled　steel　tube　of　rectangular　section　after　being　exposed　to　high　temperatures,　to　investigate　the　influence　of　temperature　on　section　capacity　and　load-deformation　behavior.　The　main　parameter　varied　is　temperature,　from　20°C　to　900°C.　A　mechanics　model　is　described　in　this　paper　for　the　behaviour　of　concrete-filled　RHS　(Rectangular　Hollow　Section)　columns　after　exposed　to　high　temperatures,　and　is　a　development　of　the　analysis　(Han　et　al,　2001a)　used　when　only　normal　temperatures　apply.　The　predicted　load　versus　axial　strain　relationship　is　in　good　agreement　with　stub　column　test　results.　Simplified　models　are　derived　for　the　section　capacities　and　the　modulus　of　elasticity　of　the　composite　sections.　It　was　found　in　general,　that　the　higher　the　exposure　temperature,　the　higher　the　loss　of　section　capacities　and　elastic　modulus　which　resulted.　The　tests　have　shown　the　importance　of　the　influence　of　high　temperatures　on　the　performance　of　concrete　filled　steel　tubes.　The　work　in　this　paper　provides　a　basis　for　further　theoretical　study　on　the　residual　strength　of　concrete　filled　steel　tubular　columns.