Abstract: AIM:To analyze the risk factors of acute ST-segment elevation myocardial infarction (STEMI) in young adults with acute myocardial infarction (AMI). METHODS: A cohort of 1137 consecutive STEMI patients admitted to our hospitals from April 1995 to May 2005 were divided into three groups according to ages: 21- to 40-year-old group (n=55), 41- to 60-year-old group (n=364) and 61- to 90-year-old group (n=718). Data on clinical cardiovascular risk factors, demographic features and angiographic findings were gathered and analyzed. RESULTS: Only 4.84% of the hospitalized STEMI patients over the 10-year period were <40 years of age. Young adults were found to be predominantly male and most had a smoking and alcohol history (P<0.01). Diabetes and hypertension were less prevalent in the group of young adults. Analysis of lipid profiles showed comparatively higher total cholesterol, low-density lipoprotein, high-density lipoprotein and triglyceride values in the young age group (P<0.01). Angiography showed a high propensity toward single-vessel involvement in the young adult group (P<0.01). In-hospital and 5-year all-cause deaths in the young age group were lower than those in older adults (P<0.01). CONCLUSION: The risk factor profile and angiographic involvement differ considerably between the high-risk young population and older adults. However, the short- and long-term prognosis in young adults is more favorable.