Twenty four eyes from 23 neovascular glaucoma (NVG) patients, who underwent trabeculectomy with 0.2 or 0.4 mg/ml MMC in least the previous 6 months, were examined in order to evaluate the mid-term effects of a trabeculectomy with mitomycin C (MMC) in NVG. Success defined when an intraocular pressure (IOP) < 22 mmHg and > 5 mmHg with or without medication was observed. The mean IOP was reduced from 46.8±12.9 mmHg preoperatively to 18.2±12.0 mmHg at the last follow-up (mean = 25.8 months). The overall success rates at 1-, 3-, 6-, 9-, and 12-months after surgery were 71%, 58%, 50%, 29%, 29% respectively. The number of anti-glaucoma medications administered was significantly reduced from 2.6±0.7 preoperatively to 0.9±1.0 postoperatively (Wilcoxon signed rank test, p = 0.005). In addition both the intraoperative MMC concentration and application time had no influence on lowering the IOP (logistic regression analysis, p = 0.228, 0.910, respectively). There was a similar incidence of postoperative complications in both the success and failure group. These results suggest that a trabeculectomy with MMC is an effective surgical procedure in NVG patients and the MMC concentration is not crucial for reducing the IOP postoperatively.