Aim: Cyclooxygenase-2 (Cox-2), the inducible key enzyme in the biosynthesis of prostaglandins, appears to play a role in the regulation of progression, invasiveness and angiogenesis of various neoplasms including some glial tumors. Little is known about the role of Cox-2 in angiogenesis and proliferation of ependymomas. We studied Cox-2 expression, Ki-67 labeling index (Ki-67 LI) and microvessel density (MVD) in 30 intracranial ependymomas and analyzed the relationship among these parameters to evaluate their importance in the tumor biology of ependymomas. Results: The mean Ki-67 LI for all tumors ranged from 1 - 50% (mean 9%). Statistically significant difference was present for Ki-67 LI between ependymomas (grade II, WHO) and anaplastic ependymomas (grade III, WHO) (p < 0.001) (mean Ki-67 LI for ependymoma, 2.8%, for anaplastic ependymomas, 15.6%). Anaplastic ependymomas did not demonstrate a greater vascularization than ependymomas, and the MVD values were 84.5 +/- 39.7 for ependymomas, and 90.6 +/- 61.4 for anaplastic ependymomas. Cox-2 immunohistochemical expression was observed in 19 tumors (63%). Although Cox-2 expression was slightly higher in anaplastic ependymomas, it was not statistically significant. No correlation was found between Cox-2 expression and MVD and Ki-67 LI. Conclusion: Similar to morphologic and prognostic heterogeneity in ependymomas, Cox-2 expression, MVD and Ki-67 LI also show a great variability. Other factors may be more important for the proliferation and angiogenesis of ependymomas.