Electroconvulsive therapy (ECT) has been in use for over 50 years and remains one of the most effective treatments in psychiatry. Effectiveness rates for ECT in depression range between 80% and 90%; no comparative study has shown any other intervention to be superior to ECT. ECT is also recommended for mania, schizophrenia and as a safe treatment for the elderly or medically ill depressed patient. This paper will deal with the use of ECT in depression. The areas to be covered are the clinical indications, the factors predictive of response, the evidence for the efficacy of ECT, as well as theories of the mechanism of its action, side effects and guidelines for prescribing the procedure. Notwithstanding the efficacy, the safety and perhaps an improved public acceptance, some observers have noted that there is a decline in the use of ECT. Others have suggested that such a decline may be evident only in the public sectors such as state and provincial psychiatric hospitals. Ongoing research is necessary to achieve further refinement of ECT, as well as enhance our understanding of this important treatment procedure.