Assisted circulation (AC) by intra-aortic counterpressure (IACP) has been used in 60 patients either pre- and postoperatively after a complication of acute myocardial infarction (25 patients: group A), or for a low-output syndrome after extracorporeal circulation (ECC) occurring in the operating theatre (20 patients: group B), or secondarily (15 patients: group C). In group A cases, the IACP stabilised a the myocardial ischaemia, and permitted coronary arteriography and subsequent surgery with little risk. Out of the 8 patients in this group who had cardiogenic shock only 4 survived, whereas out of the 17 patients without shock, only one died. Of the group B and C patients, 58% responded favourably to IACP, and 75% of group B cases survived as against 33% of group C. The postoperative low-output syndrome is related not to the ECC itself but to ischaemia of the subendocardial vasculature during surgery. The incidence of this syndrome can be reduced by the use of improved techniques of myocardial protection. AC by means of IACP becomes an effective therapeutic weapon if it is used early, or even systematically when the ejection fraction is below 0.03 and/or the EVR is less than 0.80.