Electrodiagnosis can classify hereditary motor and sensory neuropathies (HMSN) into two basic types: primarily demyelinating with secondary axonal loss and primarily axonal. For the most part, the various forms of HMSN show uniform symmetric nerve conduction slowing, in contrast to acquired neuropathies, which may be multifocal with nonuniform conduction velocity slowing and temporal dispersion. Nevertheless, there are exceptions. This article reviews the available literature and describes the electrodiagnostic approach to HMSN, detailing potential sources of error that can lead to misinterpretation of data.