A controlled study was carried out to evaluate the effect of postoperative subconjunctival 5-fluorouracil (5-FU) injections on the surgical outcomes of trabeculectomy in the Japanese (a total of 196 eyes in 157 patients). The eyes that had undergone trabeculectomy with postoperative 5-FU (5-FU group) included 36 eyes with primary open-angle glaucoma (POAG) and 17 with secondary glaucoma (SG) undergoing their first or second trabeculectomy. There were also 34 eyes with refractory glaucoma. The eyes that had had trabeculectomy without postoperative 5-FU (control group) included 46 POAG and 31 SG eyes undergoing their first or second trabeculectomy and 24 refractory glaucoma eyes. The surgical techniques and postoperative care were virtually identical between the two groups, except that the control group did not receive 5-FU. The results were analyzed by means of a life table method and a postoperative intraocular pressure (IOP) level equal to or less than 20 mmHg was adopted as the criterion for successful IOP control. In the 5-FU group, the success probability (%) at the 3-year follow-up was 93.9 +/- 4.2 (SE) for POAG eyes, 93.8 +/- 6.1 for SG eyes, and 86.7 +/- 5.6 for refractory glaucoma eyes. In the control group, it was 55.0 +/- 7.9, 37.2 +/- 13.5, and 16.1 +/- 7.4, respectively. The difference in success probability between the 5-FU and control groups was highly significant (P less than 0.001 or 0.01). In the POAG and SG eyes, the mean postoperative IOP was significantly lower in the 5-FU group than in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)