The treatment of sepsis continues to be a major problem in emergency and intensive care, and that is another reason why there has been a desire for the development of a simple diagnostic method that would yield results in the early stage. CD14 is present intracellularly and in the cell membrane of macrophages, monocytes, and granulocytes, and is recognized to be responsible for endotoxin-induced intracellular signaling. CD14 is also known to be present in the blood in the form of a soluble protein. We discovered a soluble CD14 molecule that differs from conventional CD14, i.e., a soluble CD14 subtype (sCD14-ST, 13 kD), and named it “Presepsin”. We also developed a quantitative method of determining Presepsin by an enzyme-linked immunosorbent assay, and we concluded that measuring Presepsin values of sepsis patients by this method is currently the best way to diagnose sepsis from the standpoint of diagnostic power. We have also developed a rapid semiquantitative method of measurement by a simple point of care test. In addition, at present, results can be obtained in approximately 15 min by performing a chemiluminescence enzyme immunoassay on whole blood. In the future it is expected to be widely used as a rapid diagnostic method for sepsis in clinical settings.