In the last few years matrix vesicles (M.V.) have been found in the vessel wall in various diseases and are considered to be related with pathological changes of the extracellular fibers of the tissue (atypical collagen etc.). Since the trabecular meshwork, at least the cribriform region, may be looked upon as a part of a vessel wall, it was an obvious conclusion to look for M.V. even in this area. Lysosomal and non-lysosomal M.V. were found in 138 trabeculectomy-specimens of various kinds of glaucoma, located for the most part within the cribriform or juxta-canalicular region of the meshwork. In ten cases small, electron-dense M.V. were found which ultrahistochemically showed a positive reaction for acid phosphatase. This proves that these vesicles are indeed extracellular lysosomes.