To assess the clinical significance of angiogenesis in oral squamous cell carcinoma (SCC), we examined vessel density immunohistochemically in 44 primary oral SCCs using the JC-70A antibody which reacts specifically with vascular endothelial cells. In addition, the expression of vascular endothelial growth factor (VEGF) and its receptors, KDR, Flt-1 and Flt-4 in oral SCCs was examined in relation to the vessel density and lymph node metastasis. There was no association of vessel density with tumour site, T-category (tumour size), degree of differentiation or cervical lymph node metastasis, except that the vessel density of carcinomas with a well-defined tumour-stromal boundary was higher than that of diffusely invasive carcinomas. The intensity of VEGF expression correlated with lymph node metastasis (P < 0.01), but not with vessel density. The expression of KDR and Flt-1 did not correlate with vessel density and lymph node metastasis. However, the vessel density in Flt-4-positive carcinomas was higher than that in Flt-4-negative carcinomas (P < 0.05), and expression of Flt-4 most significantly correlated with lymph node metastasis (P < 0.001). These results suggest that the expression of VEGF or Flt-4 rather than vessel density may be a predictor of lymph node metastasis in oral SCC.