Glass fiber reinforced polymer (GFRP) composite reinforcing bars (rebars) have become a viable alternative to steel rebars as reinforcement for concrete structures, particularly, in marine and corrosive environments. Several design guides have been developed to assist structural engineers with design of GFRP reinforced concrete members. Most of current practices for design of GFRP reinforced concrete members primarily adopt design values for steel reinforced concrete members, modified by the ratios of the GFRP to steel stiffness, which may work in some cases. The GFRP rebars that are available in the construction market have different long-term properties depending on several factors, e.g. type of fibers, resin, and coatings. Such varying long-term properties make it much harder to predict accurately the long-term response of GFRP reinforced concrete members using the same unified limits and design equations for all commercially available types of GFRP rebars. This paper presents critical factors that influence the design and response of GFRP reinforced concrete members. Some of the factors that this paper is focusing on are ductility, deformability, load transfer, amount of GFRP rebars, and effect of long-term properties on long-term deformations. Discussion of some experimental research results is presented, and design recommendations of various international guides are also discussed.