In addition to the previously reported experimental results on post-tensioned glass beams, the current paper discusses the results of exploratory bending experiments on 2 series of structural glass beams which are pre­stressed by externally bonded tendons. These tendons - stainless steel or CFRP - are pre-tensioned and subsequently adhesively bonded to the lower edge of the glass beams by means of a two-component epoxy adhesive (3M DP 490). After curing, the pre-stressed glass beams are tested in four-point bending and their results are compared with the experimental results of reference beams without any tendons. From the results it is observed that pre-stressed glass beams demonstrate enhanced fracture strength compared to the reference beams. In addition, the pre-stressed glass beams show significant post-fracture load­carrying capacity. From the study it is concluded that pre-stressing a glass beam with externally bonded tendons is a feasible concept. However, more in depth studies to validate the concept are needed.