We studied the efficacy and safety of using topical mitomycin C (MMC) as an adjunct to glaucoma filtration surgery. Trabeculectomy was performed in 23 eyes of 19 patients with poor surgical prognosis. After the preparation of a scleral flap, 0.2 mg or 0.4 mg/ml MMC was applied to the exposed tissue for 5 minutes. The wound was then irrigated with 250ml of normal saline. The mean follow-up period was 7.8 months. Preoperative mean intraocular pressure (IOP) was 33.8mmHg, and the mean IOPs on 1, 3, 6, and 12 months after operation were 10.3, 12.5, 12.4 and 12.3mmHg, respectively. At postoperative 12 months, 74.7% achieved an IOP of less than or equal to 20mmHg without any antiglaucoma medication. There were early postoperative complications of aqueous leaking from conjunctival wounds in 3 eyes (13.0%), shallow anterior chamber in 2 eyes, and hyphema in one eye and one eye had long-term hypotony lasting more than 3 months. Although MMC is simple to use, it is a potent adjunct to glaucoma filtration surgery, more work should follow to determine the mechanism of action, indications, dosage and optimal exposure time of MMC.