Therapeutic approaches in the practice of haematology/oncology are increasing in complexity. Agents such as the purine analogues and monoclonal antibodies may introduce a new spectrum of infection as a consequence of prolonged/profound lymphoid suppression. The use of high dose therapy with stem cells support is increasing rapidly in clinical practice. Allogeneic transplantation is associated with prolonged immunosuppression and a high potential for transplant-related mortality from infection. This has led to intense interest in strategies aimed at improved prophylaxis and treatment of infective complications. This review aims to summarize recent advances in haematological practice and the effect this has had on opportunistic infections.