Several reports have mentioned the possibility of misdiagnosing pseudoepitheliomatous hyperplasia (PEH) of the overlying mucosa of a granular cell tumor as a squamous cell carcinoma (SCC). Because of this, morphometry was applied to five granular cell tumors with PEH and five well-differentiated SCC of the tongue. In addition, ten normal tongues have been examined. The mean area, the mean perimeter and the mean diameter of the 50 largest squamous epithelial nuclei in 50 fields were found to be significantly larger in squamous cell carcinomas than in granular cell tumors and normal tongues. The shape factor of the nucleus and the mitotic activity appeared to be of no significant value in this respect.