Background Actual data regarding coronary artery disease (CAD) patients in Japan is scarce, so in the present study a large database of Japanese patients with significant CAD was constructed for analysis of the relationship between medical treatments and outcomes in this cohort. Methods and Results The present study enrolled 15,628 patients who underwent coronary angiography and were diagnosed as having significant stenosis in at least 1 coronary artery. Of these, 13,812 patients were followed up and included in the analysis: 10,626 (77%) men and 3,186 (23%) women. Diagnosis at the time of registration was acute myocardial infarction (AMI) for 2,955 patients, old myocardial infarction for 3,913 patients and unstable angina pectoris for 2,049 patients. Patients were followed up for an average of 2.7 years. At the start of the follow-up, 37.4% of the patients were prescribed statins, 50.2% calcium-channel blockers (CCB), 31.6% angiotensin-converting enzyme inhibitors (ACEI), 13.5% angiotensin II receptor blockers (ARB) and 60.2% nitrates. Univariate Cox regression model analysis showed that the hazard ratio (HR) of statins was 0.780 (95% confidence intervals (CI), 0.710-0.856; p<0.001); fibrates, 0.580 (95%CI, 0.425-0.790; p=0.001); CCB, 1.067 (95%CI, 0.976-1.166; p=0.153); ACEI, 1.062 (95%CI, 0.968-1.166; p=0.202); ARB, 1.036 (95%CI, 0.914-1.174; p=0.581); nitrates, 1.147 (95%CI, 1.043-1.260; p=0.005). When the data were adjusted for background data and all cardiovascular medications, the HR of statins was 0.809 (95%CI, 0.726-0.901; p<0.001), CCB 1.031 (95%CI, 0.937-1.135; p=0.535), ACEI 1.023 (95%CI, 0.924-1.132; p=0.663), ARB 0.991 (95%CI, 0.867-1.132; p=0.890), nitrates 1.074 (95%CI, 0.973-1.186; p=0.155). For patients presenting with AMI at the time of registration, the HR of CCB was 1.340 (95%CI, 1.084-1.655; p=0.007) and that of nitrates was 0.862 (95%CI, 0.703-1.059; p=0.157). Conclusion In a cohort of CAD patients in Japan, the prescription pattern differed from that of Western studies. Statins and fibrates were shown to be significantly beneficial in the whole cohort. In the AMI subgroup, CCB showed a deleterious effect and nitrates showed a non-significant tendency for beneficial effect, which should be investigated in future randomized control trials. (Circ J 2007; 71: 1835 - 1840)