Tumor angiogenesis is important for tumor growth and metastasis. Angiogenic activity in a tumor is usually evaluated by microvessel density (MVD), which is expressed as the number of microvessels per unit area of tumor tissue. MVD has been studied in a variety of human cancers, including head and neck cancers. However, tumor angiogenesis in mucoepidermoid carcinoma (MEC) has not yet been documented. Methods: We examined tumor angiogenesis immunohistochemically in 35 specimens of MEC. Blood vessels in sections were highlighted with the endothelial cell marker CD34. Tumor vascularity was evaluated by counting peritumoral and intratumoral MVDs. MVDs in the normal oral mucosa (NOM, n=8) and normal salivary glands (NSG, n=14) adjacent to MECs were also counted for comparison. Correlations between MVDs in MECs and the clinicopathological parameters of MEC patients were analyzed statistically. Results: CD34- positive-endothelial-cell-lined microvessels were found in NOM, NSG, and MEC samples. The mean MVD increased significantly from NOM (7.3±1.3) through NSG (12.8±1.7) to MEC (24.7±4 for peritumoral and 25.7±6 for intratumoral tissues; P=0.000). Statistical analysis showed a significant association between mean intratumoral MVD in MEC samples and clinical staging (P=0.000); MEC patients with more advanced clinical stages (stages 3 and 4) were likely to have higher intratumoral MVDs. Other correlations between mean intratumoral or peritumoral MVD in MEC samples and clinicopathological parameters of MEC patients were not significant. Conclusions: High intratumoral MVD is associated with advanced clinical stages in MEC patients.