The prognostic significance of nuclear DNA ploidy patterns and the S-phase fraction (labeling index; IL) were evaluated in 365 gastrointestinal tumors, and in 62 of them a combined analysis of DNA ploidy and the SPF was performed. For accurate evaluation, we used fresh frozen specimens, and we classified the ploidy pattern into 6 types; 1. diploid, 2. DS (diploid + high LI), 3. Notch, 4. Shoulder, 5. Tetraploid and 6. Aneuploid. Type 1 or type 2 tumors were classified as diploid, and the others were classified as aneuploid. In 103 cases of gastric cancer and 101 colon cancers due to the short observation period, but in 46 patients with operable primary liver cancer, a significant difference was observed. A high average of LI was detected in colon cancer (approximately 13%), but no relationship between LI and the ploidy pattern was found. This indicates that the LI may become an independent prognostic factor, and that the combined assay of DNA ploidy and the LI may offer a more precise evaluation of the malignant potential of gastrointestinal tumors.