In 15 pregnant women, during the last month of pregnancy, the heart of living human foetuses has been searched for with echocardiological techniques, using a multiple-crystal transducer. The single heart structures distinguished on the bidimensional image were picked out with a single ultrasonic ray and photographed with a Polaroid camera. The echocardiological image revealed of such structures is similar to that found in newborns. The aorta and the mitral valve have been registered in all cases. It has been possible, with minor frequency, to reveal the echoes of the tricuspid valve, of the interventricular septum, of the posterior wall of the left ventricle and of the pulmonary valve. The left atrium/aorta root relationship resulted almost always higher with regard to the values considered normal for newborns. The behaviour of the interventricular septum is of particular interest, as it always showed a normal movement. This report indicates that the functional load of the different heart cavities during the various phases of interuterine life is in perfect equilibrium, notwithstanding the substantial anatomical and functional modifications which occur during the course of foetal life. The Authors maintain that echocardiological methods could become indispensable in understanding the physiological and pathological aspects of foetal circulation.