In this study, we aimed to determine serum adrenomedullin levels and compare them with levels of C-reactive protein (CRP) and procalcitonin (PCT). Cancer patients aged 0-18years who experienced febrile neutropenia attacks were included in the study. Adrenomedullin, CRP, and PCT were analyzed at admission, day 3, and days 7-10 later. Fifty episodes of febrile neutropenia that developed in 37 patients were analyzed in this study. The mean age of the patients was 7.5 +/- 4.7 (1-18) years. The patients had leukemia (73%), solid tumors (19%), and lymphoma (8%). The percentages of the patients in the clinically documented infection (CDI), fever of unknown origin (FUO), sepsis, and microbiological documented infection (MDI) categories were 34%, 34%, 20%, and 12%, respectively. During the study period, four patients were lost. In the MDI group, adrenomedullin levels on day 3 were significantly higher than those in the CDI and FUO groups. PCT levels were significantly higher in the sepsis group than those in the CDI group at admission, day 3, and days 7-10. In the sepsis group, PCT levels on days 7-10days were significantly higher than those in the sepsis group. PCT values from the deceased patients on days 7-10 were significantly higher than those from patients who survived. CRP levels did not differ significantly among the febrile neutropenia groups. First, in our study, adrenomedullin was used as a biomarker in the febrile neutropenia episodes of children with cancer. Among adrenomedullin, CRP, and PCT, procalcitonin demonstrates the highest correlation with the severity of infection.