The loss of heterozygosity and mutation for nm23-H1 gene in colorectal carcinomas were studied by Southern blot and RT-PCR-SSCP/silver staining sequencing. The rate of loss of heterozygosity for nm23-H1 was 29.63%. The cases of Duke’s stage D and distant metastatsis had higher frequency of the loss of heterozygosity. No mutation for nm23-H1 was found in colorectal carcinomas. These reaults indicate that the loss of heterozygosity for nm23-H1 may play a significant role in the malignant progression and distant metastasis in colorectal carcinomas.