Distribution of mRNA expression of 1,25-dihydroxyvitamin D₃ receptor (VDR) and 25-hydroxyvitamin D₃-24-hydoxylase (24-OHase) along the microdissected rat nephron segments was examined by reverse transcription-polymerase chain reaction (RT-PCR) technique. VDR mRNA was abundantly expressed in cortical segments (glomeruli, proximal convoluted tubule, proximal straight tubule, cortical thick ascending limb, distal convoluted tubule and cortical collecting duct), and it was also detected in outer medullary segments (medullary thick ascending limb, outer medullary collecting duct). Messenger RNA of 24-OHase was abundant in proximal convoluted tubule, and it was also present in proximal straight tubule, but not in other segments. The results demonstrate that in contrast to the expression of 24-OHase mRNA which is limited to the segments where the activity of this enzyme has been demonstrated, the expression of VDR mRNA is ubiquitous along the nephron segments.