Corrosion of steel reinforcement is one of the main durability problems facing reinforced concrete infrastructure worldwide. Therefore, strengthening existing reinforced concrete structures has become one of the most important activities in civil engineering during the last decade. The main reasons for strengthening structures are to restore and enhance the load capacity, to reduce deflection at service loading, or to limit the width and distribution of cracks in concrete. Furthermore, structures often have to carry higher loads to fulfill new standards and regulations. In extreme cases, they also have to be repaired due to accidental loading. Other reasons for repairing and strengthening can be attributed to errors made during the design or construction stages, deterioration of the concrete caused by reinforcement corrosion and earthquake proof design requirements. The experimental program in this thesis consisted of 13 reinforced concrete rectangular beam specimens (2500 mm long, 170 mm wide and 300 mm deep). The program was designed to study: the effect of corrosion on the flexural behavior of reinforced concrete beams, the effect of strengthening with carbon fiber reinforced polymer (CFRP) sheets on the flexural behavior of non-corroded reinforced concrete beams, the effect of strengthening with CFRP sheets on the flexural behavior of corroded reinforced concrete beams with various degrees of corrosion, the effect of strengthening schemes on damaged beams, and the effect of load history on the behavior of strengthened beams. In general, the results of this experimental study showed that the use of CFRP sheets for strengthening reinforced concrete (RC) beams that are experiencing flexural reinforcement corrosion is capable of maintaining the structural integrity and increasing the ultimate strength of these beams to a level above the control beam. Also, the experimental study showed that the use of CFRP sheets for strengthening RC beams decrease the ultimate deflection of these beams to a level below the control beam. The results showed that the use of CFRP sheets for strengthening corroded reinforced concrete beams is an efficient technique that can maintain structural integrity and enhance the strength of such beams.