The characteristic spectrum of infections in patients with aplastic anemia, chronic neutropenic diseases, sickle cell disease, thalassemia, and other hemoglobinopathies are described. The major risk factor for infection in patients with bone marrow failure is the degree of neutropenia and monocytopenia. In patients with aplastic anemia, invasive fungal infections emerge as the major causes of mortality. Life-threatening infections are rare in patients with chronic neutropenic diseases; however, necrotizing enterocolitis due to Clostridium species may be an exception. Bacterial infections, predominantly with encapsulated bacteria, are the most common cause of death in patients with sickle cell disease, especially those who are younger than 5 years of age. Patients with thalassemia and other hemoglobinopathies are particularly susceptible to life-threatening infections with Yersinia enterocolitica as a result of iron overload or of the chelating therapy with desferrioxamine.