Piprocurarium is a curarimimetic. It is antagonized by neostigmine. Piprocurarium is strongly vagolytic, producing tachicardia. Its duration of action is shorter than that of d-tubocurare and longer than that of succinylcholine. Piprocurarium is not hypotensive, is only slightly histaminogenic, is nonirritating to the veins, and can be mixed with all the anesthetic drugs. Piprocurarium has been offered for clinical trial as a brief-acting, nondepolarizing neuromuscular blocking drug. The drug appears to be anything but short acting. A persistent tachycardia and elevation in systolic and diastolic pressure invariably follows its intravenous injection. Alarming electrocardiographic changes occur, characterized by AV dissociation, depression of the ST segment, supraventricular tachycardia and, at times, inversion of the T waves. In view of these circulatory effects, it is doubtful that the drug will be useful clinically.