This descriptive research intends to know the reason of the presence of pterigio in different population, regarding age, gender, occupation and permanence zone of Valle de San Diego de Ubate population from July 2005 to January 2006. The sample was 897 patients who attended optometry and ophthalmology consultation in the El Salvador de Ubate Hospital. The research methodology was through clinical records collection, applying a printed survey to find information about the specific problem. As a result, pterigio had a presence of 40.31% in the group of 20-40 year old population; 61.47% in 41-65 year old group and 29.22% in over 65 year old people. By gender, the prevalence was 83.64% in women and 47.36 in men. Regarding occupation, the presence of pterigio was 42.33% in people related to housework, 35.27% in agriculture and 24.18% in mining. Finally, the towns presented the following percentage: 30.24% in Ubaté, 20.16% in Fuquene, 16.13% in Susa, 11.8% in Cucunuba, Guachetá, and Carmen de Carupa, 9.7% in Tausa, 8.6% in Simijaca, and 7.5% in Suatatausa and Lenguazaque.