Paraffin embedded material from 15 patients suffering from head and neck squamous cell carcinoma (HNSCC) bordered by dysplastic mucosal areas was immunohistochemically investigated for the presence of p53 protein and Ki-67 proliferation marker. p53 protein was present in 9 cases (60%), invariably in invasive cancer areas as well as in adjacent non-invasive dysplastic mucosa. Only cells exhibiting atypia contained p53 protein. Ki-67 proliferation marker was present in the basal cells of the normal epithelium and more extensive in dysplasias and HNSCC. The presence of Ki-67 closely coincided with p53 protein in the 9 cases exhibiting this. No differences in Ki-67 expression were found between p53 positive and negative cases. It is concluded that the appearance of p53 protein occurs early in carcinogenesis but that cells also may show increased proliferation without involving immunohistochemically detectable alterations in the p53 gene.