Aim. To determine C-reactive protein (CRP) levels as diagnostic markers of infection in acute myeloid leukemia (AML) patients with neutropenia. Subjects and methods. Sixty-three AML patients (28 men and 35 women) aged 20 to 77 years (median 50 years) were examined. According to the French-American-British (FAB) classification, the types of AML were as follows: M0 (n=3), M1 (n=9), M2 (n=35), M4 (n=10), and M5 (n=6). All the patients had chemotherapy-associated neutropenia (granulocytes, less than 0.5·109/l). In different treatment steps, all the patients developed infectious complications (the study analyzed the data of 86 cases). Results. In patients with localized infections (such as mucositis, abscess, pneumonia, etc.) or fever of unknown origin (FUO), the levels of CRP were not statistically significant different, but were significantly higher than in those without infectious complications. The concentrations of CRP did not differ in patients with systemic inflammatory response syndrome (SIRS) and in those with sepsis. At the same time, the level of CRP in systemic infection (SIRS, sepsis) was significantly higher than that in localized infection (p<0.001). In patients with neutropenia, the median CRP levels were as follows: 7 mg/l (range 0-37; 95% reference interval (RI) 0 to 32) for those without infection 56 mg/l (range 13-104; 95% RI 17 to 104) for those with localized infection or FUO; and 168 mg/l (range 103-399; 95% RI 105 to 362) for those with systemic infection. Conclusion. CRP is a marker of the severity of an infectious process in AML patients with neutropenia. The increase of its level more than 32 mg/l serves a valid criterion for the presence of infection and more than 105 mg/l does for that of a systemic inflammatory response in these patients.