A review is presented of 107 cases of paroxysmal ventricular tachycardia. In the majority it was associated with acute coronary thrombosis or coronary sclerosis, in some with rheumatic valvular disease, and in others with no organic heart disease. It is generally critical and demands careful attention. Occasional cases are overlooked because only one heart sound is present for each cardiac cycle and the heart rate is misjudged to be one-half the actual rate. The outlook often is serious if the condition is not effectively treated. Therapy generally is successful in controlling the arrhythmia. The most valuable drug is quinidine. Other medications are magnesium sulfate, atropine, potassium salts, and possibly morphine.