To examine surgical effects and complications of improved nonpenetrating trabeculectomy with trabeculotomy in glaucoma patients.Glaucoma patients in two medical institutions underwent nonpenetrating trabeculectomy with sinusotomy with or without trabeculotomy, and the results were compared retrospectively in the two groups by evaluation of final intraocular pressure, drug score, and occurrence of postsurgical complications.Of the 63 eyes of 51 patients in this study, 31 were treated with nonpenetrating trabeculectomy with sinusotomy without trabeculotomy and 32 eyes were treated with nonpenetrating trabeculectomy with sinusotomy and trabeculotomy. The mean follow-up period was 17.0 months. The clinical features in both groups were similar in terms of age, presurgical intraocular pressure (P = 0.96), and presurgical drug score. The eyes treated with nonpenetrating trabeculectomy with sinusotomy without trabeculotomy had significantly reduced intraocular pressures from 21.0 +/- 4.3 (mean +/- SD) to 15.8 +/- 6.3 mm Hg (P = 0.0003) and drug scores from 2.4 +/- 1.2 to 1.6 +/- 1.1 without postsurgical complications. The eyes treated with nonpenetrating trabeculectomy with sinusotomy and trabeculotomy had significantly reduced intraocular pressures from 22.3 +/- 7.5 to 12.5 +/- 2.3 mm Hg (P < 0.0001) and drug scores from 2.5 +/- 1.9 to 0.9 +/- 1.3 without postsurgical complications. Thus, the eyes treated with nonpenetrating trabeculectomy with sinusotomy and trabeculotomy had significantly lower intraocular pressures (P = 0.016) and drug scores than did those treated with nonpenetrating trabeculectomy with sinusotomy without trabeculotomy.The authors obtained satisfactory results in reducing intraocular pressure by the combination of nonpenetrating trabeculectomy, sinusotomy, and trabeculotomy.