Our interest is in understanding the genetic bases for hereditary renal diseases of the domestic dog (Canis familiaris) and in characterizing gene loci for placement on the map of the canine genome. We report here on the cloning, sequencing and radiation hybrid mapping of the canine cDNA encoding uromodulin, a renal-specific glycoprotein. The cDNA is 2.3 kb in length and, as expected, comparisons of nucleotide sequences reveal that canine umod is quite similar to umod of other mammals. The predicted amino acid sequence of canine uromodulin has at least 70% identity with other mammalian uromodulin proteins. Canine umod has been mapped on the RHDF5000 radiation hybrid panel and positioned on the most recent canine genome map. Data indicate that umod is linked to the marker CZP2 (canine zona pellucida gene) on an RH group not yet assigned to a canine chromosome. The human umod and CZP2 genes are located on chromosome 16p13.