Aims: It is unclear how serial high-sensitivity troponin-I (hsTnI) concentrations affect long-term prognosis in individuals with suspected acute coronary syndrome (ACS). Methods and results: Subjects who underwent two hsTnI measurements (Siemens TnI Flex® Reagent) separated by 1-7 h, during a first-time hospitalization for myocardial infarction, unstable angina, observation for suspected myocardial infarction, or chest pain from 2012 through 2019, were identified through Danish national registries. Individuals were stratified per their hsTnI concentration pattern (normal, rising, persistently elevated, or falling) and the magnitude of hsTnI concentration change (<20%, >20-50%, or >50% in either direction). We calculated absolute and relative mortality risks standardized to the distributions of risk factors for the entire study population. A total of 20 609 individuals were included of whom 2.3% had died at 30 days, and an additional 4.7% had died at 365 days. The standardized risk of death was highest among persons with a persistently elevated hsTnI concentration (0-30 days: 8.0%, 31-365 days: 11.1%) and lowest among those with two normal hsTnI concentrations (0-30 days: 0.5%, 31-365 days: 2.6%). In neither case did relative hsTnI concentration changes between measurements clearly affect mortality risk. Among persons with a rising hsTnI concentration pattern, 30-day mortality was higher in subjects with a >50% rise compared with those with a less pronounced rise (2.2% vs. <0.1%). Conclusion: Among individuals with suspected ACS, those with a persistently elevated hsTnI concentration consistently had the highest risk of death. In subjects with two normal hsTnI concentrations, mortality was very low and not affected by the magnitude of change between measurements.