Percutaneous transluminal coronary angioplasty (PTCA) in patients with low ejection fraction (EF) and/or a large area of remaining viable myocardium served by the target vessel can cause hemodynamic collapse in case of acute closure. We report 11 patients in whom the cardiopulmonary bypass support (CPS) was instituted because of contraindication to surgery (Group I) or unstable angina associated with low EF and/or a large amount of myocardium perfused by the target artery (Group II). Nine were male and 2 female, mean ages of 70, with Canadian angor class I (1), II (1), or IV (9) and EF ranging from 12 to 65% (mean 34%). Thirty were the lesions to dilate; 28 were dilated successfully; in 2 an aortic dilation was also performed. One death occurred after the procedure related to collapse due to hypovolemia; another death occurred 8 months after PTCA because of pulmonary neoplasia. The other 9 patients followed-up at 1 to 8 months (mean 3.9) disclosed Canadian angor class I. The procedure's technique and the related complications are discussed. We conclude that cardiopulmonary bypass support can be used safely in patients refused to surgery and with high risk PTCA; such a procedure may expand the indication of PTCA.