Red blood cell (RBC) autoantibodies are a relatively uncommon cause of anemia. However, autoimmune hemolytic anemia (AIHA) must be considered in the differential diagnosis of hemolytic anemias, especially if the patient has a concomitant lymphoproliferative disorder, autoimmune disease, or viral or mycoplasmal infection. Classifications of AIHA include warm AIHA, cold agglutinin syndrome, paroxysmal cold hemoglobinuria, mixed‐type AIHA, and drug‐induced AIHA. Characteristics of the autoantibodies are responsible for the various clinical entities. As a result, diagnosis is based on the clinical presentation and a serologic work‐up. For each classification of AIHA, this review discusses the demographics, etiology, clinical presentation, laboratory evaluation, and treatment options. Am. J. Hematol. 69:258–271, 2002. © 2002 Wiley‐Liss, Inc.