To examine the prevalence of ocular surface disease (OSD) in glaucoma patients. This was a cross-sectional study. One hundred and one patients, 18 years of age or older, with open-angle glaucoma or ocular hypertension were consecutively recruited for the study. Patients with a history of use of cyclosporine, steroids, topical ocular nonsteroidal anti-inflammatory drugs, or punctal plugs within the last 3 months were excluded. Each patient completed an Ocular Surface Disease Index questionnaire and underwent evaluation by Schirmer test, corneal and conjunctival lissamine green staining, and tear break-up time. Using Ocular Surface Disease Index for measuring symptoms of dry eye, 60 (59%) patients reported symptoms in at least 1 eye. Severe symptoms were reported by 27 (27%) patients. Schirmer testing showed 62 (61%) patients with decrease in tear production in at least 1 eye. Severe tear deficiency was presented in 35 (35%) patients. Corneal and conjunctival lissamine green staining showed positive results in 22 (22%) patients. None had severe staining. Tear break-up time showed abnormal tear quality in 79 (78%) patients and severe decrease in tear quality was found in at least 1 eye in 66 (65%) patients. Multivariate logistic regression models were used to investigate the association between the number of benzalkonium chloride (BAK)-containing eyedrops and results on the clinical tests of OSD. After adjustment for age and sex, each additional BAK-containing eyedrop was associated with an approximately 2 times higher odds of showing abnormal results on the lissamine green staining test (odds ratio=2.03; 95% confidence interval: 1.06 to 3.89; P=0.034). A large proportion of patients with open-angle glaucoma or ocular hypertension had signs and/or symptoms of OSD in at least 1 eye. The coexistence of OSD and the use of BAK-containing medications may impact vision-related quality of life in this patient population.