C-reactive protein, a reactant of the acute phase of inflammation, has been shown to be increased in patients with unstable angina. Moreover, it has recently been found that increased C-reactive protein is associated with a poor outcome during hospitalization in selected patients with severe unstable angina. The aim of this study was to investigate the prognostic value of C-reactive protein elevation in a large population with unstable angina. We measured serum levels of this marker in 140 patients hospitalized with unstable angina (class IIIB of the Braunwald classification, mean time from last anginal episode 5 +/- 5 hours). Thirty-nine of them (28%) had increased serum levels on hospital admission and 33 (24%) experienced an adverse outcome (myocardial infarction or refractory angina) during hospitalization. Kaplan-Meier analysis showed that the probability of developing cardiac events during hospitalization was not different between patients with and without abnormal C-reactive protein levels. Furthermore, the incidence of ischemia at Holter monitoring during the first 72 hours after hospitalization was not different between patients with and without abnormal C-reactive protein. In a representative population of patients with unstable angina, a sizable proportion had increased serum C-reactive protein levels; however, abnormal concentrations of C-reactive protein do not predict an adverse outcome in the early phase after the acute episode.