An　experimental　study　was　conducted　to　investigate　the　influence　of　FRP　confinement　on　the　buckling　behavior　of　longitudinal　steel　reinforcing　bars　(rebars)　in　RC　columns　subjected　to　monotonic　and　cyclic　axial　compression.　Test　results　of　12　FRP-confined　RC　columns　and　12　FRP-confined　plain　concrete　columns　(control　specimens)　are　presented　with　particular　attention　to　the　evolution　of　strains　in　the　longitudinal　steel　rebars　and　the　FRP　jacket　as　the　load　increases.　For　an　FRP-confined　RC　column　subjected　to　monotonic　axial　compression,　the　contribution　of　longitudinal　steel　rebars　to　the　overall　axial　load　carried　by　the　column　was　deduced　by　subtracting　the　contribution　of　the　FRP-confined　plain　concrete　from　the　total　axial　load.　The　test　results　showed　that　the　compressive　stress-strain　response　of　longitudinal　steel　rebars　in　FRP-confined　RC　columns　follows　that　from　tensile　testing　before　the　axial　stress　reduces　gradually　due　to　the　onset　of　buckling　deformation.　Significant　interactions　were　found　to　exist　between　FRP　confinement　and　the　buckling　of　longitudinal　steel　rebars.　This　interaction　should　be　carefully　considered　when　formulating　constitutive　laws　for　both　the　longitudinal　steel　rebars　and　the　FRP-confined　concrete　for　use　in　theoretical　modeling.　(C)　2017　Elsevier　Ltd.　All　rights　reserved.