This chapter discusses motor evoked potentials (MEPs) recorded by transcranial electrical stimulation (TCES) and transcranial magnetic stimulation (TCMS). It describes anatomy of the central motor pathways and physiology of the D and I waves. Intraoperative monitoring of MEPs using TCES is now widely used for spinal cord and posterior fossa surgeries. Anesthetic considerations, TCES parameters, stimulation derivations, muscles utilized for MEP recordings, alarm criteria, and safety issues are discussed in detail. Even though TCMS is approved in the United States only for the treatment of depression, it has extensive diagnostic and therapeutic applications worldwide. Various diagnostic parameters of MEPs elicited by TCMS including central motor conduction time, MEP latency and amplitude, triple stimulation technique, magnetic stimulation threshold, silent period, evaluation of cortical inhibition and facilitation, long-interval intracortical inhibition, and use of paired stimuli are discussed. The TCMS parameters applied as diagnostic tools in clinical conditions such as multiple sclerosis, motor neuron disease, strokes, and myelopathies are described. Finally, some of the therapeutic applications of TCMS particularly in psychiatric disorders are discussed.