Cyclooxygenase-2 (Cox-2), the key enzyme that catalyzes the first steps in the biosynthesis of the prostaglandins from arachidonic acid, appears to play a role in the regulation of progression, invasiveness and angiogenesis of various neoplasms. We analyzed the immunohistochemical expression of Cox-2 and angiogenic parameters (microvessel density (MVD) and vascular patterns) in 54 glioblastomas. We also examined their relation with prognosis. Cox-2 immunohistochemical expression was observed in 48 tumors (89%). There was no staining in six tumors (11%). On univariate analysis, MVD was correlated with a poor outcome (MVD > 70; hazard ratio, 0.441; 95% confidence interval, 0.200-0.975, P = 0.041). But MVD showed no prognostic impact on multivariate analysis. Neither Cox-2 expression nor vascular pattern showed prognostic value. The difference in Cox-2 expression between the classical and bizarre vascular pattern in glioblastomas was statistically significant (P = 0.047). However, no correlation was found between Cox-2 expression and MVD. These findings suggest that Cox-2 is heterogeneously expressed in glioblastomas without a significant association with MVD. However, Cox-2 expression may be related to vascular pattern in glioblastomas.