This study assessed the prognostic value of cardiac troponin I (cTnI) and C-reactive protein (CRP) in unstable angina, and specifically in patients with angiographically proven coronary artery disease. These biochemical parameters, which are related to myocardial injury or to systemic inflammation, may help in short-term risk stratification of unstable angina. We prospectively studied 195 patients with unstable angina, 100 of whom had angiographically proven coronary artery disease (with normal creatine kinase [CK] and CK-MB mass). Serum concentrations of cTnI (N < 0.4 ng/ml) and CRP (N < 3 mg/L) were measured at admission, 12, and 24 hours later. The rate of in-hospital major adverse cardiac events (death, myocardial infarction, or emergency revascularization) was higher in patients with increased cTnI within the first 24 hours, regardless of the results of coronary angiography (23% vs 7%; p < 0.001). Conversely, events occurred at similar rates in patients with or without increased CRP. In patients with angiographic evidence of coronary artery disease, multivariate analysis showed that increased cTnI within 24 hours of admission (35 patients) was an independent predictor of major adverse cardiac events (odds ratio 6.7, range 1.7 to 27.3), but not cTnI levels at admission and CRP at 0, 12, and 24 hours. Thus, both in unselected patients with unstable angina and in patients with angiographically proven coronary artery disease, increased cTnI within 24 hours of admission, but not CRP, is a predictor of in-hospital clinical outcome. We also found a temporal link between cTnI increase and late elevation of CRP, suggesting that systemic inflammation may partially be a consequence of myocardial injury.