The DNA ploidy status and S-phase fraction of eight adenocarcinomas of the vermiform appendix diagnosed in Iceland during 1974-1990 were analyzed by flow cytometry. Four cases were classified as Dukes' stage B2 and four cases as Dukes' stage D. Seven tumors were diploid and one was aneuploid. The DNA aneuploid tumor was the only one which metastasized outside the abdominal cavity. The S-phase fraction in general was low. The results of this study do not indicate any significant correlation between ploidy status and clinical behavior.