Stanniocalcin is a glycoprotein hormone first described in fish as a hypocalcemic factor, and recently its mammalian counterpart has been identified. Localization of stanniocalcin 1 and its regulation of expression were determined in control and 1α,25-dihydroxyvitamin D<sub>3</sub>-treated rats. Immunoreactivity for stanniocalcin 1 was detected in the loop of Henle, macula densa cells, distal convoluted tubule (DCT), and cortical collecting duct (CCD), and also faintly in the medullary collecting ducts. Pre-embedding electron-microscopic immunocytochemistry revealed stanniocalcin 1 in the apical membrane of cells of loop of Henle, DCT, and principal cells of CCD. The expression of stanniocalcin 1 was increased by elevated plasma calcium via 1α,25-dihydroxyvitamin D<sub>3</sub> treatment. In conclusion, stanniocalcin 1 was expressed in the apical membrane of distal nephron segments and enhanced by vitamin D<sub>3</sub>.