PURPOSE: To evaluate acute retinal vein occlusion as a potential complication of trabeculectomy with mitomycin C in cases of advanced glaucoma. METHODS: The records of three patients who developed retinal vein occlusions immediately after uncomplicated trabeculectomy with mitomycin C were reviewed. RESULTS: All three patients had advanced open-angle glaucoma with total cupping of the optic nerve, severe visual field loss, and evidence of systemic vascular disease. A marked decrease in intraocular pressure was noted in the postoperative period in all of the patients. CONCLUSION: A shift in the lamina cribrosa, associated with the perioperative intraocular pressure change, may have contributed to occlusion of the venous outflow system in these susceptible patients.