We investigated the nucleotide substitution and insertion/deletion polymorphism of the HV1 region in mtDNA by sequencing blood samples from 150 unrelated Japanese and 120 unrelated Chinese and revealed 108 sequence types from the Japanese group and 87 sequence types from the Chinese. Some substitutions were characteristic of East Asian populations as compared with data reported on Caucasian populations, and some were area-specific among East Asians. The level of genetic diversity and genetic identity revealed by this system was superior to that obtained by VNTR systems for nuclear DNA. These results show the usefulness of mtDNA sequencing in forensic examination for individual identification. We also found some sequence variations in the homopolymeric tract of cytosine (np16180-16194 in the Anderson's reference sequence) that might suggest some hints regarding the mechanisms for and the development of heteroplasmic length variations in this tract.