A brief account of repetitive transcranial magnetic stimulation (rTMS) with reference to electroconvulsive therapy (ECT) is given, identifying similarities and dissimilarities, and discussing their potential therapeutic roles. The insulating properties of the skull prevent specific, noninvasive stimulation of particular brain regions by direct electrical means. ECT allows electrical stimulation of the cortex, but its concomitant seizures and distributed electrical currents can have adverse effects on patients. By contrast, magnetic fields pass almost without attenuation through the skull, and can induce secondary electrical currents in localized areas of the brain. Subconvulsive rTMS does not require seizure or general anesthetic, and does not affect memory. Recent studies suggest that rTMS has therapeutic potential for mood disorders, for which ECT is well established. rTMS is a new technology with the potential to treat some mental disorders currently treated with ECT, with fewer side effects. ECT will almost certainly remain the treatment of choice in some situations, but ECT and rTMS may be alternatives for other patients. It is possible that rTMS will become established in some areas where ECT is not used. Further research will define these roles and evaluate the utility of rTMS.