Inclusion Criteria:  age ≥ 18 years; reported or observed fever at arrival at the ED (≥38.3° C on one occasion or ≥38°C on two or more occasions within 1 h); chemotherapy-induced neutropenia (absolute neutrophil count ≤500/mm3 or ≤1000/mm3 and anticipated to decrease to fewer than 500/mm3 within 24 to 48 h).  Exclusion Criteria:  refusal to participate; prior inclusion in the study for a previous episode of FN; any intravenous antibiotic administration during the preceding 72 h; renal failure requiring renal replacement therapy or with an estimated creatinine clearance of less than 20 ml/min; palliative status with life expectancy of less than three days; pregnancy, absence of health insurance, mental deficiency or inability to understand informed consent, no French speaking; patient with a microbiological documented infection when arriving at the ED (e.g. positive blood culture).