Abstract: An alcohol extract of the seeds of Lepidium apetalum Willd. exhibited positive isotropic action on the rabbit heart in situ. It showed significant therapeutic effect in the chloral hydrate-induced heart failure in the heart-lung preparation of cat, the force of contraction of the heart improved, the minute cardiac output recovered, and the high venous pressure lowered. Its electrocardiographic manifestations bore some similarities to those of digitalis, viz., S—T segment depression and sloping downwards with a characteristic diphasic T wave, P wave also depressed. The above result suggests the existence of certain cardiotonic substance in the seeds of Lepidium.