To compare aqueous humour and plasma levels of ghrelin, a peptide recently identified in human eyes, in patients with open-angle glaucoma and controls. Cross-sectional, controlled, hospital-based study. Twenty-four open-angle glaucoma (17 primary open-angle and 7 pseudo-exfoliation glaucoma) patients and 30 controls were included. All participants were patients scheduled for cataract or glaucoma surgery. Patients with other ocular pathology, previous ocular surgery or diabetes were excluded. Blood samples were collected before elective surgery. Aqueous humour was aspirated from the anterior chamber through a paracentesis with a 27-G needle under sterile conditions before any tissue manipulation. Ghrelin quantification was performed with commercially available Radioimmunoassay kits. Ghrelin levels in aqueous humour and plasma. Plasma levels of ghrelin were 490.5 ± 156.0 pg/mL in the open-angle glaucoma and 482.2 ± 125.4 pg/mL in the control group (Mann-Whitney test, P = 0.897). Aqueous humour levels of ghrelin were 85.5 ± 15.4 and 123.4 ± 25.5 pg/mL in the respective groups (P < 0.001). The ratio of plasma/aqueous humour ghrelin concentration was higher in the open-angle glaucoma versus the control group (5.75 ± 1.92 vs. 4.00 ± 1.04, P < 0.001). There was no difference in aqueous humour levels of ghrelin between primary open-angle glaucoma and pseudo-exfoliation glaucoma patients (P = 0.494). Aqueous humour levels of ghrelin were significantly lower in open-angle glaucoma patients, compared with controls. This difference may manifest a role of ghrelin in the disease process or a consequence of antiglaucoma treatment. © 2011 The Authors. Clinical and Experimental Ophthalmology © 2011 Royal Australian and New Zealand College of Ophthalmologists.