Abstract： Objective To investigate the role of cyclooxygenase-2 (COX-2)and microvascular density (MVD) in the tumorigenesis and progression of transitional cell carcinoma of urinary bladder ( BTCC ), evaluate their clinical significance in BTCC. Methods In this study, immunohistochemistry was used to study COX-2 and the tumor interstitial vascular density in 103 cases of BTCC. And as the contrd, 13 cases of normal bladder tissue and 21 cases of chronic cystitis tissue was collected. At the same time, the numbes of the microvascular were recorded. Results The expression of COX-2 in BTCC was positively correlated to the tumor interstitial vascular density ; Both of them were related to the tumor pathologic grade, the invasiveness of the tumor tissue, the lymphatic transferation and recurrence time of tumor(P＜0.05), but not related to the tumor size or tumor number(P＞0.05). Conclusion COX-2 was overexpressed in BTCC and played an important role in oncogenesis development and recurrence of BTCC. The expression of COX-2 was positively related to the tumormicrovas- cularization.