The results of 117 trabeculectomies performed on 98 patients under the age of 50 years were reviewed. The success rate in primary glaucomas (29/39, 74%) was considerably higher than in secondary glaucomas (24/50, 48%) or in developmental glaucomas (6/17, 35%). Only one (9%) of 11 trabeculectomies performed for neovascular glaucoma was successful. Trabeculectomies for secondary glaucomas were significantly more often successful in eyes that had not undergone previous surgery. None of the six trabeculectomies performed on patients under the age of ten years controlled the intraocular pressure. Of the 45 trabeculectomies performed on patients aged 10 to 29 years, 17 (38%) were successful. Of the 66 trabeculectomies performed on patients aged 30 to 49 years, 43 (65%) were successful. The success rates among black, white, and hispanic patients were similar. The ability to identify patients at high risk for failure of trabeculectomy may be of value in guiding the surgical management of glaucoma.