Electroconvulsive therapy (ECT) is a safe and effective treatment for severe and persistent depression, bipolar disorder and schizophrenia. Though ECT is now over 60 years old, it remains an underutilized treatment today. History, patient selection, safety, and characteristics of the treatment stimulus, technique, and medications used in ECT are reviewed. Dosing strategies, as pertaining to seizure threshold, will be considered. Mechanisms of action, especially with regard to serotonin, norepinephrine, and dopamine receptor expression will be discussed.