A human genomic clone encompassing the last exon of the gene for cytochrome c oxidase subunit VIb and a human genomic clone containing the most distal end of this gene were characterized. The last exon of the gene codes for the 17 C-terminal amino acid residues of the subunit and the 3' noncoding region. Downstream from the gene we found a single base difference between the DNA sequences of the two genomic clones. An inverted Alu dimer repeat was identified further downstream.