Aim. To study the incidence and risk factors of bacterial infections and the efficiency of empirical antibacterial therapy in patients in the early period after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Subjects and methods. The study included 155 patients who had undergone allo-HSCT. Myeloablative conditioning was used in 39% of the patients. All the patients with neutropenia (NP) received antibiotic prophylaxis with fluoroquinolones until recovery of white blood cell counts or before systemic antibiotic therapy. Antibiotic therapy and a change of antibiotics were considered effective in achieving persistent apyrexia and positive clinical changes. Results. The incidence of febrile neutropenia (FNP) in the patients after allo-HSCT was 63%. The duration of grade 4 leukopenia did not depend on the conditioning regimen. Neutropenic fever was noted in 68% of the patients with NP lasting longer 10 days. In shorter-duration NP, the rate of fever was 52%. Among the patients with mucositis, the frequency of FNP episodes was significantly higher (69% versus 52%; p=0.02). The diverse spectrum of isolated bacteria was represented as gram-positive cocci in 45% of cases; Klebsiella pneumoniae and Enterobacter cloacae were more common among gram-negative ones (24%). The efficiency of empirical antibiotic therapy was 57% (25% for monotherapy, 53% for combined treatment regimens); the early mortality was 2%. Conclusion. Infection-related FNP is noted in 68% of the patients in the early posttransplantation period and the risk factors of its development are NP duration, oral colonization with pathogens, and the absence of invasive mycosis after allo-HSCT. Antibacterial prophylaxis significantly decreases the incidence of bacterial complications. Empirical monotherapy with third- or fourth-generation cephalosporins and carbapenems against infections in a transplantation patient is as effective as their combination with aminoglycosides.