Eighty-one eyes which had had trabeculectomy with a mean follow-up period of 9.2 years (range 7 to 10 years) were studied retrospectively for their subsequent pattern of intraocular pressure. Of 43 chronic open-angle glaucoma eyes, 29 (67%) had their pressures maintained below 21 mmHg by trabeculectomy alone over a 7-10-year period. On the other hand, 25 of 38 (65%) eyes with other types of glaucoma required an average of 1.5 different antiglaucoma medications post-op for the control of their intraocular pressures. Fifteen of 69 (22%) phakic eyes required cataract extraction at a mean of 5.1 years post-op. Two of 43 (5%) chronic open-angle glaucoma eyes suffered blinding complications attributable to the procedure. Seventeen percent: of eyes gained visual field at a mean of 7% of the pre-op field per year following trabeculectomy. Fifty percent lost field at a mean rate of 2.3% per year.