We reviewed records from 428 consecutive patients with severe Graves' ophthalmopathy to determine early and late results after transantral orbital decompression. Optic neuropathy was present in 217 (50.7%) patients. Post-operatively, 402 (89%) of 453 eyes with preoperative visual acuity worse than 20/20 improved or remained the same. Visual field scotomas improved or resolved in 245 (91%) of 269 eyes tested pre- and postoperatively. Preoperative papilledema resolved or improved in 99 (94%) of 105 eyes, and preoperative exposure keratitis improved or resolved in 178 (92%) of 195 eyes. Average proptosis reduction was 4.7 mm. Postoperatively, new diplopia developed in 74 (64%) of 116 patients who had no diplopia before orbital decompression, although 300 patients ultimately had strabismus surgery. At late follow-up (N = 293 patients), 226 (77%) had single vision and 44 (15%) had correction with prism. Complications included sinusitis (18 patients), lower eyelid entropion (38 patients), numb lip (23 patients), cerebrospinal fluid leaks (15 patients), and one frontal lobe hematoma (one patient). The average duration of follow-up was 8.7 years. Transantral orbital decompression effectively reduces proptosis and usually corrects optic neuropathy. In other circumstances, the benefits achieved and the side effects incurred must be carefully balanced for each patient before transantral orbital decompression is considered.