YKL-40 is a glycoprotein secreted by macrophages and neutrophils in tissues with inflammation. Plasma YKL-40 is increased in patients with coronary artery disease (CAD) and associated with cardiovascular and all-cause mortality. Furthermore, plasma YKL-40 seems related to the number of diseased main vessels in patients with stable CAD. The aim was to further study the relation between YKL-40 and stenosis degree, stenosis type and actual ischemia in stable CAD patients.