Anemia occurs in more than one half of patients with systemic lupus erythematosus and is usually attributed to "chronic disease." Approximately 10% of patients with a positive Coombs' test manifest clinically significant hemolysis. Leukopenia affects both granulocytic and lymphocytic lines and may be caused by autoantibodies. Nevertheless, enhancement of B lymphocyte function occurs in active disease, perhaps due to a loss of regulatory T cells. Most patients have increased production and increased peripheral destruction of thrombocytes, with a normal circulation platelet count. Thrombocytopenia is usually caused by increased destruction. Qualitative abnormalities of platelet aggregation also occur. Circulation anticoagulants are not rare; however, spontaneous bleeding is uncommon. The anticoagulants, immunoglobulins directed against clotting factors, assume importance for invasive procedures. Most clinically significant hematopoietic abnormalities can be suppressed by corticosteroids; however, splenectomy, or immunosuppressive agents, or both, may be indicated for patients who respond inadequately to corticosteroids.