Abstract: Liensinine, an alkaloid of the embryo loti, possesses a hypotensive activity of short duration, whereas the effects of its 2 quaternary ammonium salts are rather powerful and lasting. For O-methyl-liensinine methosulphate, the blocking effect on the ganglion of vagus nerve is more potent and durable than that on the superior cervical ganglion. Yet the vagi play no important role in its hypotension. Experiments on spinal cats and cross circulation of dog's head have demonstrated that the mechanism of action is mainly of peripheral, rather than central, origin. O-methyl-liensinine methobromide produces, likewise, a reduction of blood pressure in renal hypertensive dogs. The quaternary ammonium salts of liensinine differ from d-tubocurarine by one less ether linkage in chemical structure. Since liensinine is a novel typo of alkaloid, further study of its structure-activity relationship is of significance.