The dc gradient across the reticular lamina, which can be as large as 185 mV, represents the algebraic difference between the endocochlear potential (EP) and the negative resting potential found within the organ of Corti. During asphyxia, the decline in CM paralleled closely the decline in this dc gradient. These data suggest strongly that CM represents a modulation of both dc resting potentials. The negative resting potential was examined further. Like EP, it is most probably extracellular, since it can be recorded with glass pipettes having a tip diameter of 25 μ. It decreases as a linear function of log K+concentration in scala tympani, and it appears to be much more resistant than EP to cochlear temperature reduction.