BACKGROUND AND OBJECTIVES: The prevalence of coronary disease in Korea, with the consequent morbidity and mortality, has rapidly risen during the last two decades. This study aimed to describe the changing pattern in the demographic composition during the 1990s of patients presenting with acute myocardial infarction (AMI) in Korean metropolitan cities. SUBJECTS AND METHODS: Data from the medical record of patients with AMI, admitted to five University Hospitals in Busan and Daegu between January 1990 and December 1999, were sorted according to their age (<30, 3044, 4559, 6074, >75 years) and gender. RESULTS: During the last decade, the number of cases of AMI increased from 283 in 1990, to 988 by 1999 (ratio of AMI/medical patients admitted; 1.68% in 1990 to 2.52% in 1999). The most prevalent age group was 6074 yrs (46.1%), followed by 4559 yrs (34.2%). Generally, the male cases were twice as prevalent as female (68.2% : 31.8%), but the gender ratio was reversed in the highest age group (>75 yrs) (44.6% : 55.4%). During the period in question, the gender ratio and age distribution remained reasonably constant throughout. The proportion of younger AMI patients (<45 yrs) did not increase. CONCLUSION: Admissions due to AMI increased substantially during the 1990s. Almost half the cases were from the 6074 yrs age group, and two third were male. There were little changes in the compositions of age and gender of the AMI cases during this period.