Fiber reinforced polymer (FRP) bars have lower modulus of elasticity than steel bars. For this reason when FRP bars are used as flexural nonprestressed reinforcement in concrete sections, the stress in the FRP is limited to a relatively small fraction of its tensile strength. This limit, necessary to control width of cracks at service, governs design of the required cross-sectional area of the FRP. Parametric studies on rectangular and T-sections are presented to show that the design based on allowable strain in the FRP results in sections that exhibit large deformation before failure. The concept of deformability, given in the Canadian Highway Bridge Design Code, as a requirement in the design of sections is discussed and modifications suggested. Using the new definition, it is shown that when, in addition to the crack control requirement, an upper limit is imposed on the cross-sectional area of the FRP, no calculations will be necessary to check the deformability.Key words: fibre reinforced polymer, reinforcement, concrete, design, deformability.