Electroconvulsive therapy (ECT), which has been in use for 75 years, is an important treatment for severe and treatment-resistant depression. Although it is acknowledged as the most effective acute treatment for severe mood and psychotic disorders, it remains controversial because of misperceptions about its use and lack of familiarity among health care professionals about modern ECT technique. The authors present an illustrative case of a patient for whom ECT is indicated. They review the basic and clinical science related to ECT's mechanism of action and discuss clinical issues in the administration of a course of ECT, including the consent process.