Background High C-reactive protein (CRP) levels have been associated with higher mortality rate in patients with acute myocardial infarction (AMI). However, it is not known whether inflammation plays a role in the time-course of heart failure (HF) in this clinical setting. Our aim was to study the nature of the relationship between CRP and HF during AMI. Methods This prospective study was carried out in 269 subjects admitted to the hospital for suspected AMI. Of these, 220 had evidence of AMI. The other 49 subjects were studied as controls. CRP was assessed on the first, third, and seventh day after admission. Results CRP was significantly higher in the patients with AMI than in the control patients (P = .001) and peaked on the third day. Among the patients with AMI, CRP was higher in patients with HF than in patients without HF (adjusted P = .008, P = .02 and P = .03 on 1st, 3rd, and 7th day, respectively). Prevalence of HF on admission,was slightly higher in the subjects with first-day CRP greater than or equal to 15 mg/L than in those with CRP < 15 mg/L, and the between-group difference progressively increased from the first to the seventh day (P < .0001). At multivariable regression analysis, first-day log-CRP was shown to be a strong independent predictor of both HF progression (P < .0001) and left ventricular ejection fraction (P < .0001). One-year total mortality and HF-mortality rates turned out to be higher in, the patients with CRP = 85 mg/L than in those with CRP below that level (P < .0001), and log-third-day CRP was independently associated with 1-year mortality at multivariable analysis (P = .0001). Conclusions CRP on admission to hospital is suitable for predicting the time-course of HF in patients with AMI. Peak CRP value is a strong independent predictor of global and HF-mortality during the following year.