Composite　action　between　a　steel　frame　and　an　overlying　slab　plays　an　important　role　in　the　structure　design　of　a　beam-column　joint　in　a　steel　or　composite　framed　structure.　This　research　investigates　the　seismic　performance　of　a　joint　between　a　steel　beam　and　a　hollow　square　steel　(HSS)　or　a　concrete　filled　square　tubular　(CFST)　column　with　or　without　an　overlying　concrete　slab.　The　objective　of　this　research　is　to　evaluate　the　composite　action　between　the　steel　girder　and　concrete　slab.　Four　T-shaped　beam　to　column　joints　are　tested　under　cyclic　loadings.　The　main　experimental　parameters　are　column　type　(HSS　or　CSFT)　and　concrete　slab　(with　or　without).　Secondly,　the　seismic　behavior　of　the　joint　is　investigated　in　terms　of　failure　mode,　hysteretic　behavior,　skeleton　curve,　stiffness　degradation,　and　strain　distribution.　Plastic　deformation　is　concentrated　at　the　beam　end　and　brittle　fracture　is　effectively　avoided　in　the　vicinity　of　the　beam-to-column　joints.　All　the　tested　specimens　exhibit　excellent　energy　dissipation　capacity　and　ductility.　The　composite　action　between　a　steel　girder　and　a　concrete　slab　significantly　enhance　the　capacity　of　the　joint　in　terms　of　stiffness　and　yield　bending　moment.　The　plastic　bending　moment　capacity　is,　however,　slightly　improved.