We performed DNA flow cytometry analysis of colon carcinomas from the viewpoint of DNA heterogeneity. The materials were 25 colon carcinomas and 17 metastatic lymph nodes. Four different regions were examined in each primary tumor. The DNA index (DI) was classified into four groups. We classified the primary tumors into homogeneous and heterogeneous group according to the DI of the four regions of each case. Ten of 25 (40%) were classified as homogeneous and 15 (60%) as heterogeneous. The heterogeneous group tended to show more aggressive clinicopathologic characteristics. The corresponding rate between the maximum DI in the primary tumor and the DI in the metastatic lymph node was 65% (11/17). The maximum DI of the primary tumors was mostly seen in the metastatic lymph nodes, suggesting high metastatic potentiality of the higher DI clones. The examination of DNA heterogeneity may be useful for detecting the more precise character of the colon carcinomas. In heterogeneous cases, the higher corresponding rate of DI between primary and metastatic lesions suggested that metastasis occurred frequently in primary lesions containing gathering larger DI cells.