Pterygium is a chronic disease of unknown origin and pathogenesis. It is a vision threatening disease where surgical excision is effective. We examined surgically excised symptomatic pterygia for the presence of herpesviruses such as cytomegalovirus (CMV), herpes simplex virus (HSV) and Epstein-Barr virus (EBV) DNA using the polymerase chain reaction (PCR) technique. Samples of normal conjuctival tissue from limpus at 12 or 6 hours were excised in some of the eyes treated; they were used as controls. HSV DNA was detected in 9 and CMV DNA in 8 out of the 20 examined samples. In 3 out of the 20 examined samples both HSV and CMV DNA were detected whereas EBV DNA was not found in any of the examined samples. These results suggest that HSV and CMV may contribute to the pathogenesis of pterygium.