Hematologic abnormalities are commonly associated with infection by the human immunodeficiency virus (HIV) that is the etiologic agent of the acquired immunodeficiency syndrome (AIDS). Bone marrow examinations reveal frequent dysplasia, dyserythropoïesis, lymphocytic infiltration and plasmocytosis. These marrow morphologic characteristics are strongly associated with peripheral blood cytopenia of one or more lineage: anemia, granulocytopenia or thrombocytopenia are frequently described. The pathophysiology of these observed deficiencies is still unclear, although several mechanisms have been postulated as possible explanations for the hematological features of AIDS patients. The hematologic manifestations observed in patients with AIDS or AIDS-related complex (ARC) and the postulated pathogenetic mechanisms are discussed in this review.