We analyzed the long-term results of trabeculectomy in a homogeneous group of 90 eyes (75 patients) followed up one to five years after surgery. The effect on intraocular pressure was considered stable after one year; complete success was achieved in 69 (71%) of cases with a further in 8 (9%) partial success in eight (9%). The pressure-lowering effect was closely related to the presence of a filtering bleb. The main complication was the late appearance of lens opacities, although these seemed less frequent than after other antiglaucoma operations. Lens opacities were particularly frequent in hypotonic eyes and may depend upon the process of aqueous humor filtration itself.