There are many acquired and hereditary coronary risk factors, and the gender is known as a factor influencing the development of acute myocardial infarction (AMI). To evaluate the role of the gender in the occurrence of AMI, we compared patient backgrounds, their clinical manifestations, outcomes, and coronary angiographic findings between 390 male and 110 female AMI patients, who had been admitted to the coronary care unit (CCU) of the Tsuchiura Kyodo General Hospital and undergone coronary angiography on an emergency basis. The incidence of AMI was the highest in the age group of 60s for males, while for females in the age group of 70s. As coronary risk factors, smoking habit was more common in males, while hypertension, hyperlipidemia and diabetes meritus were more common in females. Coronary angiograms revealed no differences in the number of diseased vessels and location of infarction. Frequencies of urgent PTCA were also identical between the two groups. In clinical outcomes, elder females had poorer prognosis mainly due to a higher incidence of death caused by cardiac rupture. It has been reported that definite increase of AMI after menopause is attributable to disturbed lipid metabolism due to a reduced estrogen level. Our study showed that aged female AMI patients had poorer prognosis possibly due to associated multiple risk factors, mutiple organ disorders and delayed admission to hospital and higher risk of cardiac rupture. Therefore, in the treatment of aged female AMI patients, these tendencies must be taken into account.