Purpose: To evaluate the outcome of the second Ahmed glaucoma valve (AGV) surgery in eyes with failed previous AGV surgery. Design: Retrospective case series. Patients and Methods: Following chart review, 36 eyes of 34 patients with second AGV implantation were enrolled in this study. The primary outcome measure was surgical success defined in terms of intraocular pressure (IOP) control using two criteria: Success was defined as IOP %21 mmHg (criterion 1) and IOP %16 mmHg (criterion 2), with at least 20% reduction in IOP, either with no medication (complete success) or with no more than two medications (qualified success). KaplanuMeier survival analysis was used to determine the probability of surgical success. Results: The average age of the patients was 32.7 years (range 4u65), and the mean duration of follow-up was 21.4 months (range 6u96). Preoperatively, the mean IOP was 26.94 mmHg (standard deviation [SD] 7.03), and the patients were using 2.8 glaucoma medications on average (SD 0.9). The mean IOP decreased significantly to 13.28 mmHg (SD 3.59) at the last postoperative visit (P = 0.00) while the patients needed even fewer glaucoma medications on average (1.4 1.1, P = 0.00). Surgical success of second glaucoma drainage devices (KaplanuMeier analysis), according to criterion 1, at 6, 12, 18, and 42 months was 94%, 85%, 80%, and 53% respectively, and according to criterion 2, was 94%, 85%, 75%, and 45%, respectively. Conclusion: Repeated AGV implantation seems to be a safe modality of treatment with acceptable success rate in cases with failed previous AGV surgery.