Intra-aortic balloon counterpulsation (IABP) related complications in a heterogeneous group of patients who received an IABP before or after thrombolytic therapy and mechanical revascularization or in the management of refractory unstable angina and myocardial infarction related mechanical complications were evaluated prospectively. Ninety-one patients were enrolled to the study. Mean IABP duration was 4.3+/-2.4 days. While the IABP was in place, three patients (3.3%) had femoral artery emboli, four patients (4.4%) had lower extremity ischemia that resolved after the removal of the balloon, eight patients (8.8%) had groin hematoma requiring blood transfusion (< or =2 units) and four patients (4.4%) had intra-aortic balloon rupture. The relation of several risk factors to groin hematoma requiring < or =2 units blood transfusion, emboli, lower extremity ischemia and to total complications was evaluated. A chi-squared analysis showed that nadroparine use was more often complicated with emboli (P = 0.00005) and ischemic events (emboli and/or lower extremity ischemia) (three patients; 30% of nadroparine group vs. four patients; 4.9% of heparin group, P = 0.005) and hypercholesterolemia (>200 mg/dl) was more often complicated with lower extremity ischemia (P = 0.017). Forward conditional logistic regression analysis did not show any relation between the risk factors identified and emboli, lower extremity ischemia, ischemic events and groin hematoma (P>0.05), but an inverse relation was found between IABP duration and total complications (P = 0.0198). In conclusion, IABP related complications were found to remain unchanged but were not life-threatening and were inversely related to IABP duration and this suggests shorter periods of IABP use whenever possible and one must be cautious to use low molecular weight heparin in patients with an IABP in place.