PURPOSE: To evaluate the prevalence of pterygium and its determinants in the underserved, rural population of Iran. METHODS: In this cross-sectional study of 3851 selected individuals, 86.5% participated in the study, and the prevalence of pterygium was evaluated in 3312 participants. A number of villages were selected from the north and south of Iran using multistage cluster sampling. Pterygium was diagnosed by the ophthalmologist using slit-lamp examination. RESULTS: The mean age of the study participants was 37.3 ± 21.4 years (2-93 years), and 56.3% (n = 1865) of them were women. The prevalence of pterygium was 13.11% [95%confidence interval (CI):11.75-14.47]. The prevalence of pterygium was 14.99 (95%CI:12.79-17.19) in men and 12.07 (95%CI:10.3-13.84) in women. Pterygium was not seen in children below the age of 5 years. The prevalence of pterygium increased linearly with age; the lowest and highest prevalence of pterygium was observed in the age group 5-20 years (0.19%) and 61-70 years (28.57%). Evaluation of the relationship between pterygium with age, sex, educational level, and place of living using a multiple model showed that age, living in the south of Iran, and low educational level were correlated with pterygium. CONCLUSION: The prevalence of pterygium was significantly higher in Iranian villages when compared with the results of previous studies. This finding may represent the effect of a rural lifestyle and its risk factors.