The nm23 gene was originally identified by differential hybridization between two murine melanoma cell sublines with low and high metastatic potential. Nm23 is localized on chromosome 17q21.3-22. Allelic deletions of chromosome 17 have been related to the progression of colorectal carcinomas. We have evaluated and compared the expression of nm23 NPD kinase protein using an immunohistochemical method and DNA ploidy evaluation with image analysis. This study was performed on 20 patients, who underwent surgery for colorectal carcinoma. Patients were followed up during the period from 1992 to 1994. Results have shown an association between the parameters obtained for the nm23 NPD kinase protein expression, and aneuploid DNA and neoplastic progression. The expression of nucleoside diphosphate (NDP) kinase mm23 has been reported to be inversely related to the metastatic potential of experimental cells in human breast cancer. A relationship between the positivity in protein expression of gene product in the allele nm23 H1 and the state of the lymph nodes has also been found.