AIM: To compare the long-term intraocular pressure (IOP) outcomes of Ahmed Glaucoma Valve (AGV) implantation to trabeculectomy with mitomycin C (MMC) in open-angle glaucoma (OAG). METHODS: 78 OAG patients who underwent AGV implantation were matched with respect to age, preoperative surgery, preoperative IOP and preoperative medicines to 88 OAG patients who underwent trabeculectomy with MMC with a minimum of 3 years' follow-up. The cumulative probability of success between the two groups with different criteria was analysed: (1) an IOP < or =21 mm Hg and a reduction of IOP>/=15% from baseline; and (2) an IOP < or =18 mm Hg and a reduction of IOP > or =20% from baseline. No loss of light perception, no additional glaucoma surgery and no hypotony were also required. RESULTS: The 5-year cumulative probability of success was not statistically significant between eyes that had an AGV or trabeculectomy with MMC when success was defined as criteria A (p = 0.094). However, when success was defined according to criteria B, eyes undergoing trabeculectomy with MMC had a higher rate of success (p = 0.024). CONCLUSIONS: Trabeculectomy with MMC has a significantly higher 5-year cumulative probability of success compared with AGV implants when greater reduction IOP is necessary.