Antiplatelet therapy could prevent stent thrombosis, but may be associated with an increased risk of bleeding. Recent studies have revealed that bleeding complications are relatively frequent in patients with acute coronary syndromes. Our aim was to describe the current status of antiplatelet therapy for Japanese patients with acute myocardial infarction (AMI). The Japan AMI (J-AMI) registry is a prospective observational study that has enrolled 2,030 consecutive patients with stent thrombosis elevation myocardial infarction (STEMI) admitted to 213 participating Japanese institutions. Current antiplatelet therapy for STEMI was assessed, and the occurrence of bleeding complications (based on GUSTO bleeding criteria) and stent thrombosis was also evaluated. Additionally, the clinical course after bleeding episodes was investigated. Percutaneous coronary intervention (PCI) was done in 97.2 % of the patients, using a drug-eluting stent in 30 % and a bare metal stent in 63 % of PCI cases. A 300-mg loading dose of clopidogrel followed by its administration at 75 mg/day with aspirin was the current standard treatment for Japanese STEMI patients. In-hospital bleeding complications occurred in 1.9 %, especially in patients with severe clinical features or a history of cerebrovascular disease. Moderate to severe bleeding complications were associated with 10 deaths. The in-hospital stent thrombosis (ST) rate was 1.47 %, and loading with clopidogrel prior to PCI was significantly less frequent in patients who developed ST (P < 0.001). In conclusion, the J-AMI registry revealed that severe symptoms of STEMI increased the risk of bleeding, while delay of clopidogrel loading was associated with ST. These findings suggest the need for treatment based on risk stratification to improve the balance between the beneficial and adverse effects of antiplatelet therapy in Japanese STEMI patients.