AIMS: To determine if intraoperative application of 5-fluorouracil (5-FU) improves the prognosis for trabeculectomy in east Africa. METHODS: 68 eyes with chronic open angle glaucoma were included in a randomised trial of intraoperative 5-FU versus placebo. Main outcome measures were intraocular pressures at 6 months and probability of failure at 2 years. RESULTS: 180 days after surgery the mean intraocular pressure (IOP) was 17.4 (SD 6.1) mm Hg in the placebo group and 16.9 (5.8) mm Hg in the 5-FU group. By 2 years after trabeculectomy, the probability of successful IOP control was 70.6% in the placebo group, and 88.8% in the 5-FU group. The placebo group was 2.18 times (95% CI 0.67 to 7.15) more likely to require additional IOP lowering procedures than the 5-FU group. Among patients followed for 2 years, 30% lost 0.3 logMAR units of visual acuity. CONCLUSIONS: Trabeculectomy in Africa has an acceptable success rate which may be enhanced by the use of intraoperative 5-FU. It is estimated that this would cost approximately 1.25 pounds sterling per trabeculectomy failure prevented.