Aspirin should be used for the prevention of cardiovascular (CV) events by the risk-benefit balance. This study was conducted to clarify CV and bleeding events in Japanese aspirin users with a history of CV diseases. This study was a prospective, nationwide, multicenter cooperative registry of Japanese patients with CV diseases at risk of thromboembolism who were taking aspirin (75-325 mg) for at least 1 year. We observed major CV and bleeding events during follow-up. Patients with history of ischemic stroke (IS), transient ischemic attack (TIA), coronary artery disease (CAD), atrial fibrillation (AF), and venous thromboembolism (VTE) were included and analyzed in this sutdy. CV events included IS, TIA, CAD, CV death, angioplasty or stenting, and hospitalization because of CV disease. Bleeding events included major bleeding requiring hospitalization and/or blood transfusion. A total of 1506 patients were categorized into IS/TIA (N = 540), CAD (N = 632), and AF/VTE (N = 232). Among them, 101 patients had two or more categories. CV and bleeding events occurred in 61 (3.82%/year) and 15 patients (0.93%/year), respectively. The annual rates of CV and bleeding events were 2.81% and 0.93% in IS/TIA, 5.32% and 0.75% in CAD, 1.15% and 1.15% in AF/VTE, and 6.44% and 0.91% in two or more disease categories, respectively. The Management of Aspirin-induced Gastrointestinal Complications (MAGIC) study clarified the rates of major CV and bleeding events with long-term use of aspirin in patients with prior CV diseases in real-world clinical practice. The risk-benefit balance of aspirin was acceptable in patients with IS/TIA, CAD, and multiple CV diseases but not in those with AF/VTE.Trial Registration: The MAGIC Study is registered at UMIN Clinical Trial Registry ( www.umin.ac.jp/ctr/index-j.htm ), number UMIN000000750.