Tight-seal whole-cell patch clamp recordings were obtained in situ from supporting Hensen's cells within the intact organ of Corti of the adult guinea pig. In normal phosphate buffer solution we estimated 20-50 cells to be coupled by gap junctions to the cell under the patch pipette. In the presence of 1 mM octanol, an uncoupling agent, it was possible to identify an outward current which activated upon depolarization above -20 mV and approached saturation above 70 mV. An inward current was seen with hyperpolarizations below -80 mV. These are broadly similar to the currents of Hensen's cells in vitro. Measured differences of the underlying conductance indicate that the currents are sensitive to the procedure used to isolate cells.