There are little data on the biological and prognostic role of neoangiogenesis in squamous cell carcinoma of the oral cavity (SCCOC). In particular, the role mast cells--reservoirs of angiogenetic peptides--play in neovascularization is not clear. In this work 50 cases of SCCOC T1-3 N0-1 M0 were studied, examining the microvasal density (MVD), mast cell density (MCD), relationship between these two parameters and their relationship with the pathological clinical features. Microvessels were identified with an immunohistochemical method using pan-endothelial anti-CD34 antibody while a histochemical method was used to label the mast cells with toluidine blue on adjacent sections for each tumor sample. MVD and MCD were characterized using an image analyzer. The mean MVD was 30 +/- 17 s.d. per sample while the average MCD was 8 +/- 6 s.d. per sample. Statistical analysis comparing MVD and MCD using the Pearson method showed a direct, significant correlation between the two variables (correlation coefficient = 0.496; p = 0.000). When the carcinomas were divided into subgroups with high and low MVD and MCD--using the median counts (27 and 7 respectively) as cutoff point--no association was found with the main clinical pathological features (age, sex, tumor diameter, lymph node status, cytopathological grading). As regards the correlation with prognosis, after an median 020 months of follow-up, the subgroup of patients with tumors with high MVD presented a better overall survival at 18 months from diagnosis than did the subgroup with tumors with a lower degree of vascularization (70% vs. 45%; p = 0.049 log rank test). The data obtained suggest that mast cells play an active role in angiogenetic processes in SCCOC and indicate that MVD is a favorable prognostic factor for SCCOC patients.