We report the case of a 62-year-old woman who developed an autoanti-D after cladribine treatment. In May 2000, the patient underwent splenectomy for a stage IV-B lymphoplasmocytic lymphoma. She was transfused with ABO- and Rh(D)-matched blood. A month later, she received chemotherapy with cladribine. In February 2001, blood grouping showed her to be AB, D+ and the direct antiglobulin test was positive for IgG. An autoanti-D was identified in the eluate. Genotypic analysis confirmed the Rh phenotype of the patient as ccDEe. No hemolysis was evident, as judged by the absence of anemia, a bilirubin of 15.7 micromol/L, and lactic dehydrogenase of 412 IU/L. When an anti-D is identified in a D+ blood recipient, a passive transfer of anti-D, and an alloimmunization in a recipient with a weak D phenotype, should be ruled out. Finally, as in our case, an autoantibody is an additional possibility.