All patients with non-ST-segment elevation acute coronary syndromes who will undergo coronary angiography willing to participate in the trial will receive a loading dose of 600 mg clopidogrel at least 2 hours prior to the procedure. Eligible patients who do not meet the exclusion criteria in whom angiography reveals that PCI is planned will be randomized to receive either abciximab plus low-dose heparin, 70 units/kg, or high dose heparin (140 units/kg) plus placebo.