Our objective was to investigate the hypothesis that women on adjuvant aromatase inhibitors (AIs) for treatment of breast cancer have a higher prevalence of dry eye syndrome (DES) compared with controls.Exposure and control groups were recruited. A cross sectional questionnaire-based study was performed. Demographic data and medical histories were collected. The presence of dry eye syndrome was determined by the ocular surface disease index (OSDI). The Functional Assessment of Cancer Treatment - Endocrine Subscale (FACT-ES) was performed to investigate correlations with other side effects of AIs.93 exposure group and 100 control group questionnaires were included. The groups were similar in all demographic variables. The prevalence of dry eye syndrome was 35% (exposure) and 18% (control) (p < 0.01, OR 2.5). AIs were the only factor associated with dry eyes. The OSDI score was negatively correlated with the total FACT-ES score and positively correlated with duration of treatment.Our study is the first to use a validated questionnaire to assess for DES in this population. DES is significantly more prevalent in women on AIs compared with controls. This is a newly emerging, and easily treated side effect of AIs. Self-reporting of dry eye symptoms underestimates the prevalence of DES with AIs. We recommend routine screening of patients on AIs with the OSDI with the aim of improving patient quality of life and possibly adherence.