The idea of using the eosinophil count (EC) as a diagnostic marker for clarifying the nature of systemic inflammatory response syndrome (SIRS) belongs to K Abidi, who showed that EC could be used as a diagnostic criterion of sepsis. There are no published data to define the role of dynamic control of EC in the process of intensive therapy as a prognostic marker and indicator of severity condition in critically ill patients. The aim was to determine the informative value of EC in the development of SIRS as a biomarker of sepsis and indicator of the severity condition and prognosis of outcome in the pathological process.