The nm23 gene is now generally accepted as one of the suppressor genes for metastasis in many types of human cancer. To investigate the role of the nm23 gene in gastric cancer, we examined the expression of nm23-H1 mRNA, mutations, and loss of heterozygosity (LOH) of the nm23-H1 gene in gastric cancers. The expression of nm23-H1 mRNA was examined by Northern blot analysis in eight paired sets of specimens. The expression was higher in primary cancer specimens and metastatic lymph nodes than their corresponding normal gastric mucosa in all eight sets of specimens examined, while it was similar between primary cancer specimens and metastatic lymph nodes. The mutations of the nm23-H1 gene were examined in an additional 11 sets of specimens, including eight sets of analysed by Northern blotting, by polymerase chain reaction single-strand conformation polymorphism analysis, no mutation being found in any of the 11 sets of specimens tested. LOH of the nm23-H1 gene was also examined in additional 12 sets of specimens, among which seven (58%) specimens were informative for LOH. LOH was identified in one (14%) out of these seven informative sets. These results suggest that nm23 may not be the metastasis suppressor gene and the alteration of this gene not play an important role in the process of metastasis of gastric cancer.