The relationship between the histological grading of malignancy and the expression of vimentin and cytokeratin was studied in 43 cases of oral squamous cell carcinoma. Immunohistochemical analysis was carried out with the avidin-biotin method using monoclonal antibody anti-vimentin, and the peroxidase anti-peroxidase method using the polyclonal antibody anti-cytokeratin. All cases were classified according to the histological malignancy grading system proposed by Anneroth. All of the carcinomas were found to express cytokeratin, while 60.4% expressed vimentin. Vimentin was particularly noted in all tumors scored to have highly malignant cells.