Purpose: To determine whether clinical characteristics are correlated with increased levels of transforming growth factor-β₂ (TGF-β₂) in aqueous humor in glaucomatous eyes. Methods: Aqueous humor samples were collected from 91 glaucomatous eyes. Included were samples from primary open-angle glaucoma (POAG) in 40 eyes, (pseudo)exfoliation syndrome (EXS) in 18 eyes, primary angle-closure glaucoma (PACG) in 26 eyes and uveitis-related secondary glaucoma (SG) in 7 eyes. TGF-β₂ in aqueous humor was assessed with a specific-capture ELISA. Results: The mean concentration (± standard error) of mature (biologically active) TGF-β₂ in the aqueous humor of eyes with POAG was 293.6±33.6 pg/ml, significantly higher than that in eyes with PACG, EXS and SG: 147.5±28.1, 135.8±30.2 and 41.0±10.7 pg/ml, respectively (P=0.0006, P=0.0010 and P=0.0003; analysis of variance). The mean concentration (± standard error) of total TGF-β₂ in the aqueous humor of eyes with POAG was 1647.6±124.5 pg/ml, not significantly different from that in eyes with PACG, EXS and SG: 1482.9±148.2, 1442.7±187.8 and 1929.0±367.6 pg/ml, respectively. A multivariate analysis using logistic regression showed significant correlations between mature TGF-β₂ concentration and history of cataract surgery (P=0.0225) and the use of carbonic anhydrase inhibitors (P=0.0143). Conclusions: Our results indicate that increased levels of TGF-β₂ may play an important role in the pathogenesis of POAG.