Cell proliferation and vascularization play an important role in the metabolic functions of normal and malignant tissues. Tumor cell proliferation and density of microvessels (DM) in 33 specimens of oral squamous cell carcinoma (SCC) were assessed by immunohistochemical staining of proliferating nuclear cell antigen (PCNA) and JC/70A, respectively. Their staining patterns were compared to the clinicopathologic findings. The PCNA labeling index (LI) showed significantly higher values in advanced carcinomas (T3 and T4) (mean, 20.19 +/- 12.79) than in early carcinomas (T1 and T2) (mean, 9.58 +/- 4.01; P < 0.01). The DM (mean, 105.92 +/- 22.65) and PCNA LI (mean, 25.69 +/- 13.32) of tumors with lymph node metastasis were significantly higher than in tumors without nodal involvement (DM, mean, 72.6 +/- 24.30; P < 0.01) (PCNA LI, mean, 10.25 +/- 3.99; P < 0.001). Marginal DM values were significantly correlated and directly proportional to the mode of tumor invasion. Evaluation of PCNA and DM at the periphery of the tumor may help to identify oral SCC that have higher malignant potential.