The classification of verrucous carcinoma as an entity unto itself or as a variant of well differentiated squamous cell carcinoma is controversial. To contribute new insights into the biological behavior of this rare tumor, we applied DNA flow cytometry to three node-negative verrucous carcinomas of the oral cavity. All tumors expressed a single aneuploid cell population. One of the patients experienced three courses with local recurrence. All secondary tumors retained the initially established aneuploid clone. The development of aneuploidy is thus a cytogenetic event common to both verrucous and squamous carcinoma of the oral cavity.