PURPOSE:: To report on the concentration of lipocalin-like prostaglandin D synthase (L-PGDS) in the aqueous humour (AH) in patients with open-angle glaucoma (OAG). PATIENTS AND METHODS:: Prospective assessment in 20 patients (13 female, 7 male, mean age 74±10.6 y) who underwent surgery for OAG. AH was sampled and analyzed for L-PGDS concentration. AH from 26 patients (11 female, 15 male, 72.4±14.4 y) without glaucoma who underwent cataract surgery, served as control subjects. RESULTS:: The L-PGDS concentration in the AH sampled from the anterior chamber in the OAG group (5.9±2.4 mg/L) was significantly (P<0.001) higher than in the control group (3.3±1.3 mg/L). There were no significant differences between the concentrations of L-PGDS between the left and the right eye or between genders. CONCLUSIONS:: L-PGDS concentration in the AH of patients with OAG was significantly elevated compared with its concentration in the AH of nonglaucomatous eyes. As L-PGDS is a biologically pluripotent protein, its possible role in glaucoma warrants further examination.