1. Clinical observations were made during 135 injections of dimethyl d-tubocurarine iodide to 41 patients receiving electroshock treatment. In 10 of these patients the amount of relaxation produced by head-drop doses of d-tubocurarine chloride was compared with that produced by dimethyl d-tubocurarine iodide by methods of clinical observation and by studies of blood lactic acid levels.2. Although d-tubocurarine chloride seems to produce consistently greater relaxation when given in equivalent head-drop doses, the clinically observed difference is not sufficient to offset the hazard of severe respiratory embarrassment that is encountered with the drug.3. With administration of dimethyl d-tubocurarine iodide we saw no cases of respiratory embarrassment sufficient to warrant the use of oxygen.4. It is concluded from this study that dimethyl d-tubocurarine iodide seems to be a safe and useful drug to produce a lessening of the severity of convulsions in electroshock therapy.