Today many patients admitted with an acute coronary syndrome are already taking aspirin. Because they have symptoms despite antithrombotic therapy, these patients are presumed to be at higher risk for subsequent clinical events. In a pilot trial of antithrombotic therapy in patients with unstable angina at rest or non-Q wave infarction, 93 patients admitted within 48 h of pain were prospectively followed up for 12 weeks. On admission, 29 patients (31%) were already taking daily aspirin; 64 (68%) were receiving no antiplatelet agent. After enrollment all patients received antithrombotic therapy with either aspirin or heparin according to protocol regardless of prior aspirin use. The two groups (prior users versus nonusers of aspirin) were similar with regard to age, gender, coronary risk factors, prior antianginal medication, duration of symptomatic coronary disease, presentation with non-Q wave infarction and extent of electrocardiographic changes on admission. Quantitative analysis of coronary arteriograms (on a 0 to 10 scale) showed similar myocardium-in-jeopardy scores (JS). Follow-up events (recurrent ischemia [Isch], infarction [MI] and revascularization [Revasc]) were: (formula: see text) Aspirin users experiencing rest angina are similar to other patients with ischemic rest pain. The "resistant to aspirin" group does not constitute a subgroup that is at higher risk for cardiac events or revascularization.