We performed Molteno implant surgery in one eye each of 41 patients with uncontrolled glaucoma. Intraocular pressure was controlled (intraocular pressure less than or equal to 18 mm Hg) in 32 eyes (78%). The mean preoperative intraocular pressure was 40 +/- 13.2 mm Hg, whereas the mean postoperative intraocular pressure was 16 +/- 6.6 mm Hg. Patients were followed up for an average of 16 months after the operation. Visual acuity was unchanged in 23 eyes (56%), improved in nine eyes (22%), and poorer in nine eyes (22%). The major complications included shallow anterior chamber and hypotony in six eyes (14.6%), vitreous hemorrhage in two eyes (4.9%), retinal detachment in one eye (2.4%), and malignant glaucoma in two eyes (4.9%). Less grave complications included hyphema in four eyes (9.8%), peripheral choroidal effusion in 15 eyes (36.6%), obstruction of the tube in six eyes (14.6%), recession of the tube into the angle in two eyes (4.9%), erosion of the tube in one eye (2.4%), and Tenon's cyst formation in three eyes (7.3%).