Retrospective study of 325 tissue samples of hyperplastic aberrations of the laryngeal mucosa by means of light and electron microscopy and immunohistochemical methods has demonstrated that superficial keratinization is not important for determining changes into precancerosis or "risky epithelium" or even for the progress from hyperplastic aberrations to carcinoma. The degree of keratinization of the epithelial surface in all three forms of hyperplastic aberrations is almost the same. In grouping the hyperplastic aberrations into "precanceroses" or "risky epithelium," the following morphologic changes have to be considered as extremely important factors: the occurrence of dyskeratotic cells, the basalification of the epithelium, and the response of the organism in the form of infiltration of immunocompetent cells in the subepithelial stroma.