Two potential applications of Glass-Fiber-Reinforced-Plastics (GFRP) in civil engineering type structures are investigated: (1) GFRP rebars in concrete beams; (2) strengthening of concrete girders with epoxy-bonded GFRP plates. Six concrete beams reinforced with GFRP bars were tested for flexure and shear. The load-deflection behavior to failure and cracking behavior of these beams are discussed. It is concluded that GFRP rebars may successfully be used as reinforcing elements for concrete members. In the second part of the study, four reduced-scale girders were tested to establish the feasibility of strengthening of existing concrete girders with epoxy-banded GFRP plates, and to select an appropriate epoxy for this application. Significant increase in the ultimate capacity of the upgraded girders was observed.