A multi-institutional study was conducted to assess efficacy and safety of biapenem (BIPM), a carbapenem antibiotic, as an initial-stage therapeutic agent for febrile neutropenia (FN) in patients with hematopoietic diseases. A total of 216 patients from 25 medical institutions were enrolled in this study; of these, 204 were included in the safety analysis and 178 in the efficacy analysis. The combined (excellent and good) response rate was 67.9%, and antipyretic effect (subsidence + tendency to subsidence) was achieved within 3 and 5 days of treatment in 67.3 and 75.9% of patients, respectively. Thus, the clinical responses were gratifying. A response rate of 61.7% (37/60) was observed even in high-risk FN patients in whom neutrophil counts prior to and at 72 h after the start of BIPM were ≤100/μl. BIPM is considered to be a highly promising drug, with prompt onset of clinical benefit, as an initial-stage therapeutic agent for the treatment of FN in patients with hematopoietic diseases.