Procalcitonin (PCT) and CD64 on neutrophils (nCD64) are biological markers used to assess the bacterial nature of inflammation in critically ill patients. As a rule, these indicators correlate closely with each other, significantly exceeding the reference intervals in patients with bacterial sepsis. In some cases, the change in these indicators is multidirectional, despite the similarity of the spectrum of the PCT and nCD64 synthesis triggers. Probably, PCT and nCD64 reflect somewhat different links in the pathogenesis of sepsis. Objective — to assess the relationship of procalcitonin and nCD64 with bacteremia and severity of organ dysfunction. Material and methods. In the blood of 80 patients of ICU with severe bacterial infection (n=24) and sepsis (n=56), PCT was determined, the relative number of CD64+ neutrophils (nCD64), the presence or absence of the pathogen. Evaluation of the severity of organ dysfunction was performed on a scale of SOFA. Results. A correlation between the level of PCT and nCD64 and bacteremia, more significant for nCD64, was determined. An increase in nCD64 more than 89% suggests the presence of bacteremia with a sensitivity of 82% and a specificity of 73%. A direct correlation was found between PCT values and nCD64 and severity of multiorgan dysfunction on the SOFA scale, which is more significant for PCT. Conclusion. Thus, the laboratory indices of nCD64 and procalcitonin, which are closely correlated with each other, are not fully comparable. They reflect the development of various parts of the septic process. The first, to a greater extent, is the infectious component, the second is the severity of organ disorders as a result of the system inflammatory response. The use of tests for procalcitonin and nCD64 in the complex allows to improve the quality of examination of seriously ill patients, namely, to carry out early diagnosis of sepsis.