['Coagulation FXII is activated on contact with lipoprotein particles. It has been suggested that contact with subendothelial tissue provides an alternative biological surface for FXII activation. Our aim was to investigate whether activated FXII (FXIIa) is elevated in patients with coronary atherosclerosis, and whether disease status (acute phase or stable state) affects circulating levels of FXIIa.', 'Circulating FXIIa levels were measured in the peripheral blood of 122 patients with coronary atherosclerosis (32, stable angina; 54, unstable angina; 36, nQ myocardial infarction) and in 45 age-matched subjects (Contr).', 'FXIIa levels (median, first and third quartiles; ng/ml) were higher in patients than in Contr: 1.61 (1.26-2.02) vs. 1.34 (1.13-1.81) (p<0.01). FXIIa levels were similar among patients with stable angina [1.66 (1.23-1.91)], unstable angina [1.53 (1.21-2.04)], and nQ myocardial infarction [1.75 (1.34-2.03)]. The three groups of patients had similar prevalence for most atherothrombotic risk factors; patients with stable angina had an increased severity of coronary disease, which did not explain the different levels of FXIIa. Fasting levels of triglycerides were the best predictor of FXIIa levels in our patients.'] Do acute coronary syndromes promote prolonged in vivo FXII-dependent prothrombotic activity?