This experiment used 30 rabbits (40 normal eyes) to determine the applicability of an expanded polytetrafluoroethylene (e-PTFE) surgical membrane as a glaucoma seton. The e-PTFE membrane had 0.1 mm thickness and was cut into T-shaped pieces measuring about 2×7 mm. One end of the implant was introduced into the anterior chamber through a sclerectomy opening and the other ends were allowed to extend from the Iamellar scleral flap into the subconjunctival space. During the follew-up at the end of 8 weeks, all the eyes with an implant showed an apparent filtering bleb, while only one of 6 eyes that had undergone a trabeculectomy alone did. The location of the created filtering blebs depended on the implant position. Pestoperative inflammatory changes were unremarkable. Histologic examinations reyealed a tissue-free cystic space surrounding the e-PTFE implants which maintained their original color, thickness, pliability and size. Transmission electron microscopy showed few myofibroblast-like cells in the fibrous wall containing the implant. With scanning electron microscopy, the internal end of the implant strip had a clean surface and no adhesions to adjacent structures of the anterior chamber angle. The corneal endothelial cells were intact in the area close to the tip of the implant. Considering the clinical and histologic findings, it appeared that the e-PTFE was acceptably innocuous in the anterior segment of the eye and a convenient material as a glaucoma seton.