In the mammalian cochlea, motile properties of outer hair cells may contribute to sharp tuning and amplification. Length changes of isolated outer hair cells in response to various physical and chemical stimuli have therefore been investigated by many laboratories. The present study shows that alteration of temperature changes the length of outer hair cells of the guinea pig cochlea as much as 0.22 µm/°C. Thus, length changes in response to alterations of temperature are similar to length changes in response to other physical and chemical stimul