The Slc4 family of bicarbonate transporters comprises at least three subfamilies with differences in ion coupling (Na and/or Cl) and transport mode (cotransport, exchange). AE3 (Slc4a3) belongs to the subfamily of bicarbonate/ chloride exchangers but very little is known about its localization in most organs and its functions. Two splice variants of AE3 have been identified and based on the organ of highest expression named bAE3 (brain AE3) and cAE3 (cardiac AE3). Here, we used semi-quantitative real-time RT-PCR to test for the expression of both variants in mouse kidney and found bAE3 and cAE3 expressed. However, mRNA expression levels of bAE3 were higher. In hand-dissected nephron segments, qRT-PCR detected highest abundance of cAE3 and bAE3 in the distal convoluted tubule and lower abundance in the medullary collecting duct. Immunohistochemistry and functional experiments in isolated nephron segments as well as phenotyping of AE3 deificient mice will further elucidate its localization and function in mouse kidney.