An interesting case of recurrent paroxysmal tachycardia is presented. The patient had had a previous coronary thrombosis, leaving in its wake a residual left bundle branch block. Three episodes of paroxysmal tachycardia were observed, the longest one of sixty-three days' duration. Although ventricular origin of the tachycardia was thought to be most likely, a nodal origin was also considered. All forms of therapy were tried but only intravenous quinidine proved to be successful. Experiences with massive doses of quinidine intravenously are presented.