The findings in type 1 myopathy are reviewed. Unless myotonia is present, further diagnostic refinement will usually require muscle biopsy and possibly genetic testing. Neuromuscular transmission defects are detailed in Chapter 16 (Tests of Neuromuscular Transmission). Additional testing may include screening for a thymoma or small cell cancer. Neuropathies are dealt with at some length. Clinical examples of slowing, conduction block and desynchronisation demonstrate typical findings in a generalised peripheral neuropathy due to demyelination. The same principles allow the diagnosis of focal demyelinating neuropathies, as seen in chronic compression lesions. If the underlying pathology is degenerative, a reduced or absent sensory nerve action potential indicates a lesion peripheral to the dorsal root ganglion. Further diagnostic information will require electromyography of the muscles supplied by the affected nerve or nerve roots. These principles are considered in relation to lesions of median, ulnar, peroneal, radial, medial plantar nerves and radiculopathies.