Mechanical transduction, the transformation of cellular deformation into an electrochemical response, is essential to the survival of both cells and higher organisms. In the specialized sensory organs, mechanotransducers are responsible for the sensations of hearing, touch and vibration, local gravity, kinesthesis, and probably osmoreception. In the viscera, mechanoreception provides sensory feedback on organ volume and pressure. At the cellular level, mechanoreceptors are known to provide feedback for avoidance reactions in free-swimming protozoans and for the gravitational and tactile reactions of plants. Mechanotransducers are probably essential in regulating cell volume and cell division. The known properties of mechanotransducers can be accounted for by ion channels whose gating is controlled by membrane strain.