The complete mitochondrial DNA (mtDNA) molecules of Homo and of the common chimpanzee were sequenced. Each sequence was established from tissue of one individual and thus nonchimeric. Both sequences were assembled in their entirety from natural (not PCR amplified) clones. Comparison with sequences in the literature identified the chimpanzee specimen as Pan troglodytes verus, the West African variety of the species. The nucleotide difference between the complete human and chimpanzee sequences is 8.9%. The difference between the control regions of the two sequences is 13.9% and that between the remaining portions of the sequences 8.5%. The mean amino acid difference between the inferred products of the 13 peptide-coding genes is 4.4%. Sequences of the complete control regions, the complete 12S rRNA genes, the complete cytochrome b genes, and portions of the NADH4 and NADH5 genes of two other chimpanzee specimens showed that they were similar but strikingly different from the same regions of the completely sequenced molecule from Pan troglodytes verus. The two specimens were identified as Pan troglodytes troglodytes, the Central African variety of the common chimpanzee.