Metallocarboxypeptidase Z (CPZ), a new member of the regulatory metallocarboxypeptidases, contains a 120-residue cysteine-rich region that has 20-35% amino acid sequence identity to Drosophila and mammalian frizzled proteins. In order to gain insights into the function of CPZ, we have examined the distribution of the protein by immunohistochemistry throughout mouse development. The expression of CPZ peaks at E9-E12, decreases in late gestation and falls further in adult tissues. CPZ expression in amnion cells, cochlear epithelial cells and surrounding mesenchyme, ventricular lining cells in the brain and cartilagenous condensations and surrounding connective tissue in ribs remains at high levels throughout mouse gestation. The expression pattern of CPZ overlaps with the expression pattern of several Wnt genes, consistent with the putative role of CPZ in Wnt signaling.