Objective: Acute coronary syndrome (ACS) has becomemore frequent in the elderly population due to increased lifeexpectancy. The aim of this trial was to determine clinical andlaboratory factors related to in-hospital mortality in patientsover 80 years of age who presented with ACS.Methods: A total 171 patients (86 men, median age 83 years)who were over 80 years of age and were hospitalized due to adiagnosis of ACS were enrolled in this study. The patients’ demographicdata, clinical features, and laboratory values werescreened retrospectively from hospital records.Results: During the follow-up period, 19 of 171 patients(11.1%) died. The causes of death were cardiogenic shock(n=6, 31.5%), acute renal failure (n=6, 31.5%), arrhythmia(n=4, 21%), and septic shock (n=3, 15.7%). ST-segment elevationmyocardial infarction presentation was more commonamong those who died [14 (73.7%) vs. 31 (20.5%); p<0.001].Patients who died during in-hospital follow-up also had higherpeak troponin [3.1 ng/mL (7.2) vs. 0.3 ng/mL (1.6); p<0.001]and creatine kinase-MB levels [96.7 ng/mL (194) vs. 10.9 ng/mL (36.2); p<0.001]. The results indicated that a high GlobalRegistry of Acute Coronary Events (GRACE) risk score [oddsrisk (OR): 1.074, 95% confidence interval (CI): 1.039–1.110;p<0.001], ejection fraction (EF) ≤40% (OR: 8.113, 95% CI:1.101–59.773; p=0.040), or no use of an angiotensin-convertingenzyme inhibitor (ACEI)/angiotensin receptor blocker(ARB) (OR: 0.075, 95% CI: 0.006–0.995; p=0.049) was significantlyassociated with in-hospital mortality.Conclusion: Presentation with a high GRACE risk score, nouse of an ACEI/ARB, and a low EF at admission were associatedwith in-hospital mortality in ACS patients more than 80years old.