This paper exemplifies both the shear strengthening capacity and modes of failure of Reinforced Concrete (RC) rectangular shear beams bonded externally with Bi-Directional Carbon Fibre Reinforced Polymer (CFRP) Composites. In total, 16 beams were cast without any internal shear reinforcement. Out of this, four beams were preserved as control specimens, six specimens were precracked and repaired with CFRP strips (i.e. precracked/repaired beam) and the following six specimens were strengthened without the application of preloading or precracks (i.e. initially strengthened specimen). The variables examined in the experimental investigation were the longitudinal tensile reinforcement ratio, shear span to effective depth ratio, spacing of CFRP strips, and amount and orientation of CFRP strips. All beams were tested under simply supported condition. Tests result shows that the effectiveness and shear capacity of the CFRP strengthened specimens. The shear enhancement of the CFRP strengthened beams varied between 11% and 139% over the control beam. This study confirms that the CFRP strip technique significantly enhances the shear capacity of reinforced concrete shear beams. The experimental results of the shear-CFRP strengthened beam were compared with the theoretical results. © 2007 Elsevier Ltd. All rights reserved.