Pterygium is not just a degenerative disease, but may be a proliferative disorder of the ocular surface. The etiology of pterygia has intrigued researchers for centuries. Several surveys have consistently shown that countries nearer the equator have higher rates of pterygia. A possible reason for this geographic variation is that (ultraviolet) UV B light may be a risk factor for the development of pterygia. UV B radiation may induce cellular changes in the medial limbus of the cornea. Several case-control and cross-sectional studies have attempted to accurately quantify UV light exposure and document its relationship with pterygia. Genetic attributes and other lifestyle behaviors may also contribute to the development of pterygia. However, further research efforts are needed to enable us to better understand the relative contribution of the different risk factors and how each risk factor may be linked to pterygium formation. In addition, the underlying mechanism of the effects of UV radiation needs to be further evaluated. By readdressing these unresolved issues in a newly proposed epidemiological study, new measures might be taken to reduce incidences and improve clinical managements of diseases, in addition to preventing UV exposure by eliminating other contributory factors. Meanwhile, preventive measures such as protection of the eyes by the wearing of sunglasses with UV B protective lenses and brimmed hats outdoors are recommended.