PURPOSE: Recent measurements show organ-of-Corti (OoC) motions that do not fit the classic hypothesis that outer hair cells (OHCs) amplify by pushing on the basilar membrane (BM) through stiff Deiters cells. One particularly surprising motion is that far below the best frequency (BF), the transverse motion of the OHC bottom is much greater than BM or reticular lamina (RL) motions. METHODS: We explore this with (1) data from seven gerbils showing that the ratio, Rohc, of transverse motions at the OHC top to the OHC bottom is small at low frequencies but large near BF and (2) a heuristic model for the impedances of structures in a transverse cut through the OoC (the TOoC model) that accounts for Rohc. RESULTS: The key idea is that when OHCs cyclically squeeze/expand, they force fluid out/into the space surrounding the OHCs which changes the local OoC area. At each time instant, cortilymph flows longitudinally along the tunnels from where OHCs squeeze to where OHCs expand, which is one-half the traveling-wave wavelength, λ. The impedance seen by OHCs for forcing cortilymph out/into and along the tunnels is termed Z CONCLUSION: Cyclic OHC forces produce OoC area changes consistent with those hypothesized to drive traveling-wave amplification. Z