Infections in recipients of hematopoietic stem cell transplantation (HSCT) continue to pose a major problem to the transplant and infectious disease community alike. Strategies employed to prevent bacterial, fungal, and viral infections, as well as treatment strategies once infection is established, is discussed. Included in the article are the recommendations of the Centers for Disease Control/Infectious Diseases Society of America and the American Society of Blood and Marrow Transplantation for the prevention of opportunistic infections in HSCT recipients, along with an evidence-based grading of both the strength and quality of each recommendation.