Abstract： PCR-RFLP and DNA sequencing were used to investigate mitochondrial DNA tRNA Leu (UUR)gene/ND-1gene mutations at five positions (nt3243,3316,3394,3593 and 3714) in 102 cases with early-onset type 2 diabetes mellitus and 104 healthy controls in Chinese Han population. Mutation at nt3714 A→G was first reported in patients with early-onset type 2 diabetes mellitus. There was significant difference between the two groups in the 3316 G→A mutation frequency (P<0.05).The mutation at nt 3316 in DNA ND-1 gene might play a role in the interactions between some nuclear DNA and environmental factors in Chinese early-onset mitochondrial diabetes