Fifty-two cases of autoimmune hemolytic anemia (AHA) were observed within a series of 1203 patients (4.3%) with chronic lymphocytic leukemia (CLL) followed at a single institution. Nineteen were observed at the time of CLL diagnosis and 33 during the clinical follow-up. Ninety percent of the patients with CLL/AHA showed active CLL and 25% had been treated previously. The antierythrocyte autoantibody (AeAb) was an IgG in 87% of cases and an IgM in 13%. A lymphocyte count more than 60 x 10(9)/L (P <.00001), age above 65 years (P <.01), and male gender (P <.01) emerged as independent parameters that correlated significantly with an increased rate of AHA at CLL diagnosis. Patients previously treated with chlorambucil (CB) plus prednisone (PDN) and with fludarabine plus PDN showed a similar rate of AHA (1.8% and 2.5%, respectively). After steroid therapy associated with CB in case of active CLL, 70% of patients achieved the complete disappearance of the AeAb. The actuarial AHA relapse-free survival probability was 54% at 5 years and the median survival probability after AHA was 41 months. Infections represented the main cause of morbidity and mortality. IgG AHA and the occurrence of AHA at the same time of CLL diagnosis emerged as independent factors significantly correlated with a better survival probability of AHA/CLL patients. Taken together, this study indicates that in CLL, AHA is a rare event with no independent effect on survival for which steroids, associated with CB if required, and a careful management of infections may successfully control the 2 conditions. Cooperative studies are needed to better define the optimal steroid schedule and the therapeutic role of other immunosuppressive agents and splenectomy. (Blood. 2000;95:2786-2792)