Using the patch-clamp technique, we investigated chloride channels on the basolateral membrane of the connecting tubule (CNT) and cortical collecting duct (CCD). We found a ~10-pS channel in CNT cell-attached patches. Replacing NaCl by Na-gluconate in the pipette shifted the reversal potential by +25 mV, whereas NMDG-chloride had no effect, indicating anion selectivity. On inside-out patches, we determined a selectivity sequence of Cl^- > Br^- ~ NO₃^- > F^-, which is compatible with that of ClC-K2, a ClC chloride channel present in the distal nephron. In addition, the NPo measured in cell-attached patches was significantly increased when the calcium concentration or the pH in the pipette was increased, which is another characteristic of the ClC-K. These findings strongly suggest that this channel is underlain by ClC-K2. A similar chloride channel was found in CCD patches. Since CNT and CCD are heterogeneous tissues, we studied the cellular distribution of the chloride channel using recording conditions (KCl-rich solution in the pipette) that allowed us to detect simultaneously chloride channels and inwardly rectifying potassium channels. We detected chloride channels alone in 45 and 42%, and potassium channels alone in 51 and 58% of CNT and CCD patches respectively. Chloride and potassium channels were recorded simultaneously from two patches (4% of patches) in the CNT and from no patch in the CCD. This indicates that chloride and potassium channels are located in different cell types that we suggest may be the intercalated cells and principal cells, respectively.