This paper presents the test results of an experimental study that investigates the durability of a new generation of Glass Fiber Reinforced Polymer (GFRP) bars. A total of 60 GFRP bars were embedded in concrete prisms and exposed to ten environmental conditions for 6 and 12 months. The environments included exposure to ordinary tap water, sea water, and alkaline solution at two temperatures (room and 50°C). The environments also included two typical field conditions of the Kingdom of Saudi Arabia (Gulf area and Riyadh area). The performance of the GFRP bars was evaluated by conducting tensile tests on the bars extracted out of the concrete specimens after exposure to the environmental conditions. After 12 months of exposure, the test results showed that the tap water at 50°C had the maximum effect on the tensile strength of the GFRP bars. The two field conditions did not show any harmful effect on the tensile properties of the bars after 12 months of exposure.