Background— Cardiac troponin T (cTnT) elevation is common and is a predictor of outcomes in patients with acute heart failure (AHF). The degree and progression of cTnT release during hospitalization of patients with AHF is unclear. We evaluated the incidence of cTnT release during AHF hospitalization and the relationship of cTnT release with outcomes. Methods and Results— The P lacebo-controlled R andomized study of the selective A(1) adenosine receptor antagonist rolofylline for patients hospitalized with acute heart failure and volume O verload to assess T reatment E ffect on C ongestion and renal func T ion (PROTECT) pilot study was a multicenter, double-blind study of patients with AHF. Measurements of cTnT were collected at randomization and days 2, 3, 4, and 7. Patients were classified on the basis of their serum cTnT levels at baseline: positive (>0.03 ng/mL), detectable (>0.01 ng/mL), and negative (≤0.01 ng/mL). A detectable cTnT level developed during the study (after baseline) was classified as cTnT conversion: 288 patients were included; 172 (60%) patients had detectable cTnT levels and 97 (34%) had positive values (>0.03 ng/mL) at baseline. Of the 116 patients with negative troponin at baseline, 24 (21%) had elevated cTnT levels by day 7. On multivariable analysis, positive cTnT at baseline was an independent predictor of the composite end point of cardiovascular/renal rehospitalization or death at 60 days (hazard ratio, 1.84; 95% confidence interval, 1.04–3.26; P =0.036). Kaplan-Meier curves showed similar worse outcomes in patients with troponin conversion and positive troponin at baseline. Conclusions— There was a high prevalence of baseline cTnT elevation in this cohort; 21% of those negative at baseline converted to detectable levels by day 7. Positive troponin at baseline, and conversion to positive levels, were associated with worse outcomes at 60 days. Clinical Trial Registration— URL: http://www.clinicaltrials.gov . Unique identifiers: NCT00328692 and NCT00354458.