The long-term efficacy of trabeculectomy in controlling intraocular pressure (IOP) has been found unsatisfactory in various complicated and refractory glaucomas. The most common cause for failure is excessive scarring at the filtering site. Several wound modulating agents which reduce scarring have been tested. In this study, 5-Fluorouracil (5-FU), a halogenated pyrimidine analogue and a potent anti-mitotic agent, was applied for seven days after trabeculectomy in eighteen complicated and unsuccessful filtering glaucomas, at a daily dosage of 5 mg in the form of 0.5 ml subconjunctival injections. The common postoperative complications encountered were corneal epithelial erosion (38%), wound leakage (16%), subconjunctival haemorrhage (32%) and hyphaema (10%), all during the first 7 to 10 days. Monitoring at regular intervals up to six months showed adequate control of IOP (less than 22mm Hg.) in 88% of the cases. Cases of aphakic glaucoma and neovascular glaucoma showed poor response. Use of 5-FU as an adjuvant to filtering surgery in various complicated glaucomas improves the long-term results