Clopidogrel in combination with aspirin has been a standard therapy for patients who have undergone percutaneous coronary intervention. The present study was conducted as a postmarketing surveillance, for the purpose of assessing the safety and efficacy of clopidogrel in real clinical practice in patients with non-ST-segment-elevation acute coronary syndrome (NSTE-ACS). Subjects were registered between March 2008 and December 2010, and as a result, patients not only with NSTE-ACS but also other types of ischemic heart diseases were enrolled. Data on off-label subjects were used only in safety evaluation. After excluding patients with inappropriate clinical report forms, 3,673 patients with non-ST-segment-elevation myocardial infarction, unstable angina, STEMI, stable angina, or old myocardial infarction were observed for safety evaluation. Efficacy was assessed in 2,562 of the 3,673 patients with NSTE-ACS. Aspirin was concomitantly prescribed to 3,615/3,673 (98.6 %) of the safety group, and 2,374/3,673 (64.6 %) received a loading dose of clopidogrel. During a maximum follow-up period of 12 months, 397 (10.8 %) of the 3,673 patients experienced adverse drug reactions (ADRs), of whom 145 (4.0 %) had serious conditions, as classified by the investigators. The most frequently observed ADRs were hepatobiliary and gastrointestinal disorders. Bleeding adverse events were observed in 138 patients (3.8 %) and 80 cases (2.2 %) were considered as serious. The 1-year cumulative incidence of major adverse cardiovascular events and major adverse cardiac and cerebrovascular events in the patients with NSTE-ACS were estimated to be 11.6 and 12.2 %, respectively. Serious AEs that substantially affect the safety profile of clopidogrel were not confirmed.