['Macrophages in atherosclerotic plaques secrete YKL-40. We tested the hypothesis if high serum YKL-40 concentration predicts coronary events and death of patients with stable coronary artery disease (CAD).', 'During the 2.6 years follow-up period (median 2.77 year, interquartile range 0.23 year), 270 patients among the 4298 patients with stable CAD in the CLARICOR trial suffered myocardial infarction (MI) and 377 died (187 classified as cardiovascular death). Serum YKL-40 transformed as Y=log[max(82, serum YKL-40/microg/L)] was significantly associated with cardiovascular death [hazard ratio (HR) = 1.88, 95% confidence interval (CI) = 1.54-2.31, P < 0.001], all-cause mortality (HR = 2.01, 95% CI = 1.75-2.31, P < 0.001), and MI (HR = 1.38, 95% CI = 1.13-1.68, P = 0.002). Following multivariable adjustment for cardiovascular risk factors (age, sex, previous MI, smoking status, hypertension, diabetes mellitus) and selected medical treatments Y contributed significantly to prediction of all-cause mortality (P < 0.001) and cardiovascular mortality (P = 0.001), but not MI (P = 0.25).'] Is high serum YKL-40 concentration associated with cardiovascular and all-cause mortality in patients with stable coronary artery disease?