In bony fish, stanniocalcin is a glycoprotein hormone thought to be an important regulator of calcium uptake from the aquatic environment. Although stanniocalcin was previously thought to be unique to fish, recent evidence has indicated the existence of a human homologue. To facilitate studies of the function of stanniocalcin in mammals, we have now isolated the mouse stanniocalcin cDNA. This cDNA encodes a predicted protein of the same length as its human counterpart and with a high level of similarity (238/247) amino acids are identical, and five represent conservative changes). As in human, the mRNA is expressed in many mouse tissues, suggesting that mammalian stanniocalcin has a paracrine rather than endocrine role.