There are at least three transcriptionally active human ADP/ATP translocase genes. We have isolated seven ADP/ATP translocase pseudogenes from recombinant human genomic libraries. Each pseudogene sequence had more than 85% identity with the sequence of the human ADP/ATP translocase cDNA derived from fibroblast mRNA, but each had mutations that precluded synthesis of a functional protein. Using an intron probe derived from a partial clone of the human fibroblast ADP/ATP translocase gene, we localized the gene to chromosome Xq13----Xq25-26. The gene encoding the skeletal muscle translocase has previously been shown to be on chromosome 4. Therefore, the human ADP/ATP translocase genes are members of a multigene family that includes pseudogenes and has been dispersed to at least two chromosomes.