AIM: To study the status of hMLH1 gene point mutations of gastric cancer kindreds and gastric cancer patients from north China, and to find out gene mutation status in the population susceptible to gastric cancer. METHODS: Blood samples of 120 members from five gastric cancer families, 56 sporadic gastric cancer patients and control individuals were collected. After DNA extraction,the mutations of exon 8 and exon 12 of hMLH1 gene were investigated by PCR-SSCP-CE, followed by DNA sequencing.RESULTS: In the five kindreds, the mutation frequency was 25% (5/16) for the probands and 18% (19/104) for the non-cancerous members, which were significantly higher than the controls (P＜0.01 x2 = 7.71, P＜0.01 x2 = 8.65, respectively). In the sporadic gastric cancer, the mutation frequency was 7% (4/56), which was similar to that (5/100) in the healthy controls. The mutation point of exon 8 was at 219 codon of hMLH1 gene (A-G), resulting in a substitution of Ile-Val (ATC-GTC), whereas the mutation of exon 12 was at 384 codon of hMLH1 gene (T-A) resulting in a substitution of Asp-Val (GTT-GAT), which were the same as previously found in hereditary nonpolyposis colorectal carcinoma.CONCLUSION: The members of gastric cancer families from north China may have similar genetic background of hMLH1 gene mutation as those of hereditary nonpolyposis colorectal carcinoma.