Neutropenic sepsis is a common clinical problem in hematological patients receiving intensive chemotherapy. Complications will develop in a minority of these patients. Biomarkers can be used for the recognition of infection as well as to estimate its severity and risk of complications and also to assess treatment response. Experience gained from other patient groups or sepsis patients treated in intensive care units cannot be directly extrapolated to hematological patients. Numerous biomarkers of infections have been investigated in hematological patients, but no optimal marker has been found. C-reactive protein is still the most commonly used biomarker in hematological patients, but procalcitonin may be a real challenger, although more studies are still needed.