The DNA index (DI), defined as the ratio of the G0/G1 channel number of tumor cells to the G0/G1 channel number of stromal cells, was analyzed in 121 aneuploid colorectal cancers. In patients with aneuploid tumors, a high DI significantly correlated with tumor penetration beyond the proper muscle layer, positive vascular invasion, and the presence of liver metastasis. This observation led us to conclude that a high DI is likely to be associated with hematogenous dissemination in aneuploid colorectal cancer.