Purpose: To evaluate the prevalence and characteristics of pterygium in small communities along the Solimões and Japurá rivers, State of Amazonas, Brazil. Design: cross-sectional study. Methods: This study was carried out on populations of the Brazilian Amazon rainforest. Data were collected by two separate ophthalmologists in three expeditions, covering 55 local communities. A total number of 1295 patients were examined, of which 659 were over 18 years old. The patients diagnosed with pterygium answered a questionnaire addressing gender, age and outdoor activity. Pterygium lesion sizes were graded as grade 1 (lesion covers until limbus), grade 2 (lesion covers cornea by 2 mm), grade 3 (lesion surrounds the pupil) and grade 4 (lesion crosses the pupil). Results: Pterygium prevalence was 21.2% for the overall population and 41.1% in those over 18 years old. Patients between 40-50 years old were most affected by pterygium. Pterygium data distribution by gender showed that 57.8% were men. The majority of the patients diagnosed with pterygium was active outdoors (89.5%). Subjects affected in both eyes were 75.6%. Of the total population positive to pterygium the majority was grade 1 (44%) and 2 (48.7%). Most of the patients (85%) developed nasal pterygium. Conclusion: This study shows one of the highest prevalences of pterygium in the world, covering a Brazilian region never studied before.