Cytostatic chemotherapy of hematological malignancies is often complicated by neutropenia, which increases the risk of infections, especially if the neutrophil count is below 500/µl. Frequently, fever is the first, and in most patients the only, sign of an infection. Unexplained fever is defined as follows: temperature of ≥38.3°C or ≥38.0°C for at least 1 hour, or measured twice within 12 hours, if the neutrophil count is