All pterygia have similar histologic features of solar degeneration seen in the skin such as acanthosis, keratosis, or hyperkeratosis. Although the pathogenesis of pterygia is still unclear, an association with solar exposure, in particular with UV radiation, has been reported. Telomerase activity has been found to be higher in some degenerative, precancerous, and cancerous skin lesions. We investigated telomerase activity in the epithelium and the stromal tissues of the pterygium. Pterygeal tissues were obtained from 30 patients. Telomerase activity was measured with TRAPeze-ELISA kit. Three of the 28 (10.7+) pterygeal stromal tissues demonstrated positive telomerase activity. Fourteen of the 27(51.9+) epithelial tissues were positive in telomerase activity, whereas telomerase activity was positive in only 3 of 9 normal epithelia (33.3+). Telomerase activity in the pterygium-covered epithelium was increased as compared with that seen in the normal epithelium, but the increase was not statistically significant. In conclusion, telomerase activity was somewhat increased in pterygeal tissues. Telomerase activity may be involved in the pathogenesis of pterygium.