Four consecutive cases are reported in which pars plana vitrectomy was used to treat eyes with blood-induced glaucoma complicating vitreous hemorrhage after cataract surgery. Vitrectomy resulted in removal of the posterior reservior of cells and cellular debris and cured the elevated intraocular pressure in 3 eyes. One eye required a second glaucoma procedure and long-term acetazolamide therapy. The excised vitreous was examined microscopically with several techniques, including use of a millipore filter to concentrate the cellular elements combined with a modified Papanicolaou staining technique, routine staining of sections of millipore filters, and routine staining of vitreous processed in a celloidin bag. These techniques showed variable proportions of erythrocytes, erythrocytic debris, free hemoglobin, ghost erythrocytes and macrophages containing erythrocytic debris and hemosiderin.