The hematologic manifestations of HIV infection and AIDS are common and may cause symptoms that are life-threatening and impair the quality of life of these patients. The most important of these manifestations are cytopenias. Anemia and neutropenia are generally caused by inadequate production because of suppression of the bone marrow by the HIV infection through abnormal cytokine expression and alteration of the bone marrow microenvironment. Thrombocytopenia is caused by immune-mediated destruction of the platelets, in addition to inadequate platelet production. The incidence and severity of cytopenia are generally correlated to the stage of the HIV infection. Other causes of cytopenia in these patients include adverse effects of drug therapy, the secondary effects of opportunistic infections or malignancies, or other preexisting or coexisting medical problems that may be prevalent in the HIV-infected population. Diagnosis of the mechanism and cause of the cytopenia may allow for specific management. Optimal management of the underlying HIV infection is essential, and mild cytopenia in asymptomatic patients may need no specific management. Supportive care for anemia includes the use of erythropoietin in addition to the judicious use of red blood cell transfusions. Therapy for neutropenia includes the use of the myeloid growth factors G-CSF and GM-CSF. Immune-mediated thrombocytopenia may be treated with a combination of zidovudine, corticosteroids, IVGG, and splenectomy. Platelet transfusions are sometimes needed for the treatment of thrombocytopenia caused by decreased production. Other hematologic manifestations such as hypergammaglobulinemia and lupus anticoagulants are commonly asymptomatic and usually require no specific therapy, but they can rarely cause morbidity and require specific interventions.