Determination of CRP consentrations is extensively applied to monitor and control the treatment effect on bacterial and viral infections, chronic inflammatory, oncological diseases, as well as surgical, gynecological and other complications. The article includes data on the structure and functions of CRP – multifunctional acute phase protein, playing a key role in inflammation, protection against xenogenic agents and autoimmune processes. The information on diagnostic significance of CRP in acute diseases and by treatment effect control of chronic conditions is presented. Detailed consideration of routine laboratory application of hs CRP, high-sensitive method of CRP determination, as well as of the diagnostic significance of CRP "baseline concentrations", is given.