Dry eye syndrome (DES) is believed to be one of the most common ocular problems in the United States (US), particularly among older women. However, there are few studies describing the magnitude of the problem in women and how this may vary with demographic characteristics. Cross-sectional prevalence survey. we surveyed 39,876 US women participating in the Women's Health Study about a history of diagnosed DES and dry eye symptoms. we defined DES as the presence of clinically diagnosed DES or severe symptoms (both dryness and irritation constantly or often). We calculated the age-specific prevalence of DES and adjusted the overall prevalence to the age distribution of women in the US population. We used logistic regression to examine associations between DES and other demographic factors. The prevalence of DES increased with age, from 5.7% among women or = 75 years old. The age-adjusted prevalence of DES was 7.8%, or 3.23 million women aged > or = 50 in the US. Compared with Whites, Hispanic (odds ratio [OR] = 1.81, confidence interval [CI] = 1.18-2.80) and Asian (OR = 1.77, CI = 1.17-2.69) women were more likely to report severe symptoms, but not clinically diagnosed DES. There were no significant differences by income (P([trend]) =.78), but more educated women were less likely to have DES (P([trend]) =.03). Women from the South had the highest prevalence of DES, though the magnitude of geographic differences was modest. Dry eye syndrome leading to a clinical diagnosis or severe symptoms is prevalent, affecting over 3.2 million American women middle-aged and older. Although the condition is more prevalent among older women, it also affects many women in their 40s and 50s. Further research is needed to better understand DES and its impact on public health and quality of life.