Cyclooxygenase(COX)-2 is an enzyme engaged in the synthesis of prostaglandin(PG) and is upregulated by inflammation. It is related with the expression of the vascular endothelial growth factor(VEGF) in the angiogenesis of granulation tissue. By using immunohistochemical stains, the expressions for COX-2 and VEGF were evaluated according to the degree of inflammation and the type of lesion, and the correlation between the expressions were investigated in the 39 periapical lesions (7 periapical granulomas, 7 periapical granulomas with epithelium, 25 periapical cysts) and 13 dentigerous cysts. The expression rate of COX-2 in histiocytes of periapical lesions(97.4%) was significantly higher than that of dentigerous cysts(69.2%)(p=0.0032). The expression rate of VEGF was highest in plasma cells in the periapical lesions(69.4%) and in dentigerous cysts(69.2%). COX-2 expression rate in endothelium and VEGF expression rate in epithelium were significantly higher in the periapical cysts than in the periapical granuloma and. VEGF expression rate in endothelium of the periapical lesions was increased in cases with resolving inflammation. For the periapical lesions, epithelial expression of COX-2 and VEGF showed a positive relationship(p=0.0301), and endothelial COX-2 expression revealed positive relationship with VEGF expressions in epithelium(p=0.0008), in histiocytes(p=0.0136), and in endothelium(p=0.0439). According to these findings, as the periapical lesion progressed from granuloma to cyst, the expressions of COX-2 and VEGF were increased. COX-2 expression was significantly correlated with VEGF expression, which suggests that COX-2 seems to be involved in the progression of periapical lesion by inducing the expression of VEGF.