Isolated fragments of renal tubules were prepared by treating rabbit kidneys removed from animals on a normal diet with proteolytic enzymes. The intracellular potential of tubule cells was measured either by impaling cells across the luminal membrane at the everted end of the tubule or by impaling cells across the basolateral membrane along the shaft of the tubule. The mean intracellular potential recorded from 163 cells at the everted ends of proximal tubules was -49 +/- 12 mV (SD) compared with a mean value of -29 +/- 9 mV (SD) recorded from 199 cells along the shaft of the tubules. In papillary collecting ducts there was no significant difference between the intracellular potential of cells at the everted end of the tubules compared with those of cells along the shaft of the tubule. However, two distinctly different types of intracellular potentials were recorded from collecting duct cells regardless of the location of the cells: 93 cell impalements gave a mean intracellular potential of -15 +/- 8 mV (SD), whereas 135 cell impalements gave a mean potential of +24 +/- 12 mV (SD). The data presented in this paper demonstrate that intracellular potentials can be recorded from isolated renal tubule fragments of papillary collecting ducts and proximal convoluted tubules.