The authors report on a modificaioon of goniotrepanation according to Fronimopoulos where only the trabecular network is trepaned and the sclera is closed twice (trepano-trabeculectomy). The experiences, based on 172 operations of this kind showed, that the quick restoration of the anterior chamber after the operation reduces the postoperative complications. However, like the goniotrepanating operation the effect of the regulation of the intraocular pressure is based on the formation of a small filtering bleb. The operation is especially suitable for the treatment of primary glaucoma of adults.