It has been reported that women with acute myocardial infarction (AMI) have a higher short-term mortality rate than men, but the reason is unclear and it is not known if it also applies to unstable angina pectoris (UAP). In addition, most previous studies have not presented angiographic findings. In the present study, the findings from 1,408 patients with AMI (group A: 361 women, 1,047 men) and 332 patients with UAP (group B: 103 women, 229 men) who underwent coronary angiography within 30 days of onset were analyzed. In both groups, the women were older and had a higher rate of hypertension and a lower rate of smoking than the men. There was no significant difference in Killip class or the number of diseased vessels between the women and men in both groups. Interventions (coronary angioplasty and coronary artery bypass grafting) were performed less frequently in the women than in the men (87.2% vs 91.8%, p=0.04) in group A, but not in group B (80.6% vs 81.2%, NS). In both groups, the overall mortality rate during hospitalization was higher in women than in men (group A: 14.4% vs 7.4%, p<0.0001, group B: 7.8% vs 1.7%, p=0.007). Multivariate analysis revealed that female gender was an independent predictor of in-hospital mortality in group B (odds ratio (OR): 6.4, 95% confidence interval (CI) 1.1-37.0, p=0.04), but not in group A (OR: 1.7, 95%CI 0.98-2.9, p=0.06). The independent predictors of in-hospital mortality, other than female gender were age, prior congestive heart failure, prior cerebrovascular disease and a higher Killip class in group A, and in both groups a higher number of diseased vessels. In conclusion, Japanese women with acute coronary syndromes present with similar angiographic findings and hemodynamics, but have a higher in-hospital mortality than male patients. Our results suggest that older age may be a potential explanation for the higher in-hospital mortality in women with AMI, but female gender itself may be an important predictor for it among those with UAP.