Intercalated cells of the distal nephron secrete either H+ or HCO3-. We have succeeded in isolating HCO3- -secreting intercalated cells from the rabbit kidney. When seeded onto collagen-coated permeable supports, these cells form monolayers with a resistance of 595 +/- 75 omega.cm2. The monolayers maintain the characteristics of an epithelium, with apical microvillae and tight junctions. They display the same polarity as do HCO3- -secreting intercalated cells in vivo, namely apical peanut lectin binding and apical Cl- -HCO3- exchange. The monolayers are capable of transepithelial HCO3- transport via this exchanger. The rate of Cl- -dependent transepithelial HCO3- transport is 4 +/- 0.4 nmol.min-1.cm-2. Transepithelial HCO3- transport is completely abolished by 50 microM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid applied to the apical side of the monolayer. These cultured HCO3- -secreting intercalated cells should prove useful for defining the cellular regulation of HCO3- secretion.