Efficacy and Safety in Patients With Acute Coronary Syndrome Without ST-Segment Elevation

Inclusion Criteria: * Patients aged above 20, admitted to hospitals with symptoms suspected to represent an acute coronary syndrome defined as unstable angina or acute MI without ST segment elevation greater than 1 mm are eligible for the study if they meet the following criteria: * (1)Clinical history consistent with new onset or worsening pattern of characteristic ischemic chest pain occurring at rest or with minimal exercise (lasting longer than 5 minutes or requiring sublingual nitroglycerin for the relief of pain within 24 hours before registration). * (2)Patients who meet either of following criteria * ECG changes compatible with new ischemia \[e.g. ST depression (at least 1 mm), T wave inversion (at least 2 mm), or hyperacute peaked T waves in 2 contiguous leads\]. * already elevated CK at least twice the upper limit of normal or CK-MB or Troponin I or T above the upper limit of normal or positive qualitative test for Troponin T. * (3)A percutaneous coronary intervention is planned within 96 hours after the first study drug administration Exclusion Criteria: * A)Factors that affect participation in study: * (1)Previous disabling stroke * (2)Previous intracranial hemorrhage or hemorrhagic stroke * (3)Severe co-morbid condition such that the patient is not expected to survive 1 month * (4)NYHA Class IV heart failure * (5)Uncontrolled hypertension * (6)Requirement for use of oral anticoagulants, non study antiplatelet agents (including ticlopidine) or NSAIDs (excluding unum sumatur), during study period, * B)Factors related to ASA and/or ticlopidine treatment: * (1)Use of ticlopidine within 1 week prior to randomization * (2)History of ASA or ticlopidine intolerance or allergy * (3)Contraindications to ASA or ticlopidine