A clinical-histologic and morphometric study on 32 patients with precancerous laryngeal lesions was carried out. Two biopsies taken at different times were studied, and the cases in which carcinoma developed were compared with those cases in which it did not. The only clinical-histologic variable with prognostic value, related with evolution to carcinoma, was severe dysplasia. The Malignancy Grading System, which grouped together 13 clinical-histologic variables, had both high sensitivity and high specificity. On the other hand, quantitative microscopy was a more sensitive and objective method. Through the relationship between the parameters of orientation/nuclearity and Histometric Progression Index, we could separate those cases in which invasive carcinoma developed from those cases in which it did not with a sensitivity of 100% and a specificity of 82%.