FENAMATE compounds have been reported to inhibit ion channels in a number of tissues, including a non-selective cation channel in the mammalian outer hair cell (OHC). We have further investigated the effects of 3′-5-dichlorodiphenylamine-2-carboxylic acid (DCDPC) on OHC currents using the whole-cell configuration of the patch clamp technique. Extracellular application of 10μM DCDPC rapidly and reversibly activated an inward current at hyperpolarized potentials. The DCDPC-activated current appeared in the shorter OHCs from the basal turns of the cochlea. The reversal potential of the inward current was dependent on the external K+ion concentration. An outwardly rectifying K+ current, found predominantly in OHCs from apical turns, was reversibly inhibited by DCDPC. These results suggest that DCDPC has a significant effect on OHC physiology at all tonotopic locations along the basilar membrane and so may have implications for cochlear function during fenamate intake.