Three-point flexure tests on the webs of 12 pultruded Glass Reinforced Plastic (GRP) Wide Flange (WF) specimens are described. The webs of the specimens were tested with their ends either simply or semi-rigidly supported. Dual knife-edge fixtures and rigid steel supports were designed and fabricated to simulate these support conditions. A series of low load tests were carried out on the webs of the WF specimens for both types of end conditions and deflections and strains were recorded at mid-span. Using simple beam analysis models in conjunction with the test data, both the transverse elastic modulus of the web and the rotational stiffness per unit length of the web-flange junctions of each specimen were determined. The webs of five of the specimens were failed under simply supported end conditions and the remaining seven under semi-rigid end conditions. From these failure tests the initial failure strengths of the web-flange junctions and the ultimate bending strengths of the webs were determined. The failure loads and modes of failure for both sets of end conditions have also been quantified.