ECT (electro-convulsive therapy) has been used for the treatment of depressive patients. First it was applied in patients only with sedatives without muscle relaxants, but now we employ muscle relaxants to avoid convulsion and its complications. It is called modified ECT (mECT). General anesthesia using muscle relaxant for ECT is now increasingly employed in Japan. Furthermore, there are some reports that ECT is effective not only in depressive patients but in chronic pain patients. This is why anesthesiologists are especially interested in ECT. In this chapter, clinical application, equipment and complications of ECT are discussed.