Infectious complications remain a limiting factor to hematopoietic stem cell transplantation. Infections are related to a variety of risk factors, including the type of transplant and preparative regimen, the serologic status of the donor and recipient, the presence of graft versus host disease, and numerous environmental factors. Preventive measures should emphasize provision of a protective environment, appropriate use of prophylactic anti-infective agents, and meticulous attention to infection prevention practices, such as hand hygiene, device management, and visitation regulation. After transplantation, immunizations and lifestyle issues should be addressed to minimize late infectious complications.