Bone marrow transplant recipients remain at risk for infections for a variable period of time even after adequate hematologic reconstitution. Late infections are a significant cause of morbidity and can be fatal in 4-15% of these patients. Patients with chronic graft versus host disease (GVHD) and unrelated-donor transplant recipients, even without GVHD, are at particular risk. Most late infections occur in the first post-transplant year, the majority are caused by bacteria, particularly encapsulated organisms, or herpes group viruses (CMV and VZV) and present with cutaneous, sino-pulmonary or systemic involvement. Effective chemoprophylaxis is available only for the encapsulated bacteria (penicillin or erythromycin) and Pneumocystis carinii (trimethoprimsulfamethoxazole). Routine use of long-term I.V. immunoglobulin supplementation has not been shown to be effective and may be harmful as it may delay reconstitution of humoral immunity. Active immunization (pneumococcal vaccine, influenza vaccine and HiB) can be effective in patients more than 6-12 months from transplant who do not have GVHD. In this review we present our experience, a summary of published literature on the subject of late infections in bone marrow transplant patients and offer guidelines for preventative strategies.