The impact of mechanical deformations on the electronic structure and electronic transport properties of materials is of both fundamental and applied interest. One example of this is the recent development of strained silicon by the semiconductor industry, which leads to increased carrier mobility and improved transistor performance. Another example is the intense research and development work in the area of Micro ElectroMechanical Systems (MEMS). Carbon nanotubes are particularly promising for Nano ElectroMechanical Systems (NEMS) because of their high structural strength, small size, high aspect ratio, and small weight. As we will see in this chapter, device demonstrations in this area include actuators, oscillators and electromechanical memories. Further development of these devices requires a detailed understanding of the impact of mechanical deformations on the electronic structure of carbon nanotubes. Thus, before embarking on a discussion of nanotube electromechanical devices, we first present a discussion of the impact of mechanical deformations on nanotube electronic properties, which arises because of coupling between ? and ? orbitals, and by changing bond lengths and bond angles. The behavior is rich, and depends in exquisite detail on the chirality of the carbon nanotubes and on the type of mechanical deformation. In Section 5.1, we discuss the impact of bending on the electronic properties of carbon nanotubes. In Sections 5.2 and 5.3, we discuss the change in bandgap under uniaxial strain and radial deformation, respectively. Recent examples of devices based on electromechanical response are discussed in Section 5.4.