Fiber　reinforced　polymer　(FRP),　particularly　those　incorporating　carbon　fiber　(CFRP),　has　high　strength,　high　stiffness-to-weight　ratio　and　high　resistance　to　corrosion,　which　shows　potential　for　use　as　prestressing　tendons　in　corrosive　environment.　However,　concrete　beams　prestressed　with　FRP　tendons　have　showed　brittle　flexural　failure　due　to　the　elastic　rupture　of　FRP　tendons.　In　order　to　improve　the　ductility,　a　combination　of　bonded　and/or　unbonded　prestressing　tendons　was　used.　Nine　prestressed　concrete　beams　were　tested　up　to　failure　to　study　the　effect　of　bonded　and　unbonded　FRP　tendons　on　their　flexural　capacity.　Three　factors　were　taken　into　consideration;　the　bonding　condition　of　CFRP　tendons,　the　location　of　CFRP　tendons　and　the　prestressing　ratio.　Also　an　analytical　investigation　was　carried　out　to　extend　some　flexural　capacity　calculation　equations　to　this　beam　type.　The　results　of　the　experimental　showed　that　under　the　same　condition,　the　carrying　capacity　of　concrete　beam　prestressed　with　bonded　FRP　tendons　was　20%　higher　than　that　of　internal　unbonded　prestressed　beam,　and　was　40%　higher　than　that　of　external　unbonded　prestressed　beam　without　deviators.　By　combination　of　bonded　and　unbonded　FRP　tendons,　the　ductility　of　prestressed　concrete　beams　can　be　improved.