Objective: To investigate the mutations in the D-loop region of mitochondrial DNA (mtDNA) in gastric cancer.Methods: The mtDNA of D-loop region was amplified by PCR and sequenced in 20 samples from gastric cancer tissue and adjacent normal membrane. Results: There were 7/20(35％ ) mutations in the mtDNA of D-loop region in gastric cancer patients. There were four microsatellite instabilities among the 18 mutations. Nine new polymorphisms were identified in 20 patients. Conclusion: The mtDNA of Dloop region might be highly polymorphoric and the mutation rate is high in patients with gastric cancer.