Study objective Previous studies in clinical trial populations have demonstrated that patients presenting with positive troponin levels have a higher risk of mortality than patients with later positive troponin levels, but the influence of the timing of troponin elevation has not been previously characterized. We evaluate the impact of the timing of troponin elevation on clinical outcomes and adherence to the American College of Cardiology/American Heart Association acute care guidelines for patients with non–ST-segment elevation acute coronary syndromes. Methods We examined inhospital outcomes and use of acute (<24 hours) medications and invasive cardiac procedures in 23,184 high-risk patients with non–ST-segment elevation acute coronary syndromes (positive cardiac markers or ischemic ST-segment changes) during 2001 to 2002 from 396 US hospitals participating in the Can Rapid Risk Stratification of Unstable Angina Patients Suppress ADverse Outcomes with Early Implementation of the American College of Cardiology/American Heart Association Guidelines (CRUSADE) Initiative. Baseline and peak troponin values were recorded and were designated as positive if above the cutoff value used at each institution to designate definite myocardial necrosis. Results In the study cohort, 53.2% of patients presented with baseline positive troponin levels, 30.6% had baseline negative/later positive troponin levels, and 16.2% had negative troponin levels during the entire hospitalization. Patients with baseline positive troponin levels had a higher risk of inhospital mortality than patients with baseline negative/later positive troponin levels (6.5% versus 4.1%) and were less likely to undergo early cardiac catheterization or percutaneous coronary intervention. The use of acute aspirin (in approximately 91% of patients), heparin (85%), and β-blockers (78%) was similar in patients with baseline-positive versus later-positive troponin levels. Conclusion These findings demonstrate that evidence-based therapies and interventions for non–ST-segment elevation acute coronary syndromes are underused in patients with elevated troponin levels, but baseline troponin elevations, which are associated with a higher risk of inhospital mortality, do not stimulate more aggressive care.