In case of a patient suffering from pigment glaucoma trabeculectomy was performed on both eyes. In one trabecular section the outer wall of Schlemm's canal, and in the other the trabecular framework were investigated by scanning-electronmicroscopy. The intertrabecular spaces were largely blocked by pigment granula, which, in some places, were stored in the clump cells of the iris. Even the outer wall of Schlemm's canal was dotted with pigment granula. The scanning-electronmicroscopic findings revealed the pigmental drainage blocking of the aqueous humour and explained the acute pressure rise in the pigment glaucoma with wide iridocorneal angle by an acute obstruction of the already largely blocked intertrabecular spaces.