PURPOSE. To assess the 10-year incidence of pterygium and associated factors in adult Chinese. METHODS. The population-based, longitudinal Beijing Eye Study, which included 4439 subjects (age: 40+ years) in 2001, was repeated in 2011 with 2695 subjects participating (66.4% of the survivors). Eyes with a pterygium in 2001 (n = 90) were additionally excluded. The study participants underwent a detailed ophthalmic examination, including slit-lamp examination for detection of pterygia and corneal photography for measurement of the pterygia. RESULTS. Incident pterygia were detected in 157/5300 eyes (2.9 +/- 0.3%) of 129/2628 persons (4.9 +/- 0.4%). In 101 (78.3%) subjects, the incident pterygia had occurred unilaterally. Of 44 participants with unilateral pterygium in 2001, six (13.6%) subjects developed an incident pterygium in the fellow eye during the 10-year follow up. In the age groups of 40 to 49, 50 to 59, 60 to 69, and 70+ years, the 10-year incidence of pterygia was 5.4 +/- 0.7%, 4.7 +/- 0.7%, 4.5 +/- 0.8%, and 5.0 +/- 1.5%, respectively. The length of pterygium was 30.4 +/- 14.7% of the corneal diameter. In multivariate analysis, the 10-year incidence of pterygia was associated with the rural region of habitation (P < 0.001; odds ratio [OR]: 0.24; 95% confidence interval [CI]: 0.14, 0.42) and lower fasting blood concentration of glucose (P = 0.009; OR: 0.82; 95% CI: 0.71, 0.95), whereas the level of education (P = 0.90), cognitive score (P = 0.64), occupation as farmer versus nonfarmer (P = 0.47), diastolic blood pressure (P = 0.11), and systolic blood pressure (P = 0.10) were not significantly associated. CONCLUSIONS. The 10-year incidence of pterygium in adult Chinese was 4.9%. It was significantly associated with the rural region of habitation and lower fasting blood glucose concentration. (Invest Ophthalmol Vis Sci. 2013; 54: 1509-1514) DOI:10.1167/iovs.12-11183