Background: Although mast cells (MCs) have been implicated in promoting angiogenesis in some malignant tumors, especially of the aerodigestive tract, little is known in oral squamous cell carcinoma (SCC). Methods: A retrospective study was conducted to elaborate upon the correlation between MCs and tumor angiogenesis in 26 cases of oral SCC, six cases of oral pre-malignant dysplasia, 10 cases of oral hyperkeratosis, and six cases of normal oral mucosa by means of immunohistochemical technique. Results: The MCs in all lesions and normal oral mucosa strongly expressed tryptase. The densities of MCs and microvessels appeared to increase with disease progression. The MC and microvascular counts were significantly higher in oral SCC than in hyperkeratosis and normal oral mucosa (P < 0.05). A significant correlation between MC and microvascular densities was observed in oral SCC (r= 0.5; P= 0.012). Conclusions: These findings suggest that MCs may upregulate tumor angiogenesis in oral SCC, perhaps via MC tryptase.