Ki-67 is a nuclear antigen expressed in G1, S, G2 and M phase of cell cycle and absent in quiescent cells (G0). In some neoplasms, Ki-67 expression has a prognostic value. The purpose of this study was to determine the role of Ki-67 expression like prognostic factor in oral squamous cell carcinoma (OSCC). Monoclonal antibody MIB-1 that recognizes Ki-67 antigen was used. 74 OSCCs were analyzed. 49% of OSCCs did not express Ki-67 antigen. In the Ki-67 positive tumours, the expression was slight in 36.5%, moderate in 10.8% and intense in 10.8% of the cases. In all the positive OSCCs, the distribution of the marking was patchy in different zones of the tumour, moreover, in 65% of the lesions, the positive cells were located mainly in the proximity of intraoral blood vessels. A significantly more intense expression was noted on tumours that had not been differentiated (p < 0.05), with a larger nuclear pleomorphism (p < 0.05) and in lesions that invaded in the form of disassociated neoplastic cells of in small groups of neoplastic cells (p < 0.001). However, the expression of Ki-67 did not correlate with the mitosis count and it had no influence on survival.