BACKGROUND The long-term efficacy and safety of filtering surgery with 5-fluorouracil (5-FU) in eyes with neovascular glaucoma are unknown. METHODS Kaplan-Meier survival curve analysis of surgical outcome was performed on all 34 patients (34 eyes) enrolled from May 1982 through April 1986 in the original pilot study of filtering surgery with 5-FU. RESULTS Success rates at the 1-, 2-, 3-, 4-, and 5-year intervals were 71%, 67%, 61%, 41%, and 28%, respectively. The median filter survival time was 38.7 months (95% confidence interval: 32-45 months). Twelve (35%) of 34 patients lost light perception vision, and phthisis bulbi developed in 8 (24%) of 34 patients. Age of 50 years or younger (P < 0.0001) and type 1 diabetes (P = 0.0004) were significant risk factors for surgical failure. The 1-year success rate for patients no older than 50 years of age was 23% compared with a 95% success rate in patients older than 50 years of age. After adjustment for age, type 1 diabetes was a borderline risk factor (P = 0.06). CONCLUSIONS There is a high risk of long-term failure of filtering surgery with 5-FU in neovascular glaucoma. Patients 50 years of age or younger have an extremely poor prognosis. Patients older than 50 years of age have initial short-term success with an accelerated failure rate after 3 years.