The putative copper and ATP-binding domains of the human Menkes disease gene were used as probes to screen a human liver cDNA library at reduced stringency. Sixty-five clones which remained positive after tertiary screening were subcloned and sequenced. One of these cDNA clones contains an open reading frame with 65% amino acid homology to the Menkes protein. Southern blot analysis localizes this cDNA to the region of the Wilson disease locus on chromosome 13. This cDNA detects a 7.5 kB transcript which is present in human liver and cell lines devoid of the Menkes transcript and which is absent in liver from a patient with Wilson disease. These data suggest that this cDNA is a candidate gene for Wilson disease and that the protein encoded at this locus is a member of the P-type ATPase family.