Background: Patients with acute coronary syndromes (ACSs) who present with atypical symptoms other than chest pain are frequently misdiagnosed and under-treated. Although many studies have described the association of aging and gender with atypical symptoms, few studies have examined the predictors of atypical symptoms in younger and older patients separately. Purpose: This study was conducted to examine and compare the factors associated with atypical symptoms other than chest pain in younger (<70 years) and older (>=70 years) patients with ACS. Sample and Method: Data were obtained from electronic medical records of patients who were newly diagnosed with ACS and hospitalized at C University hospital in G-city from 2004 to 2005. A total of 931 data including 626 younger (67.2%) and 305 older patients (32.8%) were used for bivariate and multivariate analysis. Results: The 58% (n=540), 18% (n=168), and 24% (n=223) of patients were ST-segment elevation myocardial infarction (STEMI), non-ST-segment elevation myocardial infarction (NSTEMI), and unstable angina (UA) respectively, and 9.7% (n=90) had atypical symptoms other than chest pain. Older patients were more likely to have longer hospital stay and less likely to have a number of risk factors for cardiovascular disease compared with those of younger patients (p<.001). Older patients were more likely to have indigestion or abdominal discomfort (p=.019), nausea or vomiting (p=.040), dyspnea (p<.001) and less likely to have chest pain (p=.007) and arm or shoulder pain (p=.018). Logistic regression analysis showed that after adjustment for gender and ACS type, diabetes (OR 2.494, 95% CI 1.528-4.071, p< .001) and hyperlipidemia (OR .486, 95% CI .285-.828, p= .008) significantly predicted atypical symptoms in younger patients. In older patients, the histories of stroke or cerebral infarction (OR 3.441, 95% CI 1.357-8.729, p< .009) and COPD or asthma (OR 2.783, 95% CI 1.004-7.710, p= .049) were positive predictors of atypical symptoms. Conclusions: Health care providers should have more concern diabetic younger persons, and older persons with chronic concomitant diseases such as stroke and COPD when evaluating patients with no chest pain.