Twenty-two patients with squamous cell carcinoma of the oral cavity were treated intra-arterially with epirubicin and cisplatin. Biopsies were taken before, during, and after treatment and analysed by DNA flow cytometry. Clinical response to therapy was better in the diploid group as well as in previously aneuploid tumors which showed complete disappearance of the abnormal clone in the course of treatment. Poor reduction of tumor volume corresponded with persistence of aneuploid cells.