Eosinophilia induced by nucleoside analogs has been described in a handful of case reports and during the treatment of both chronic lymphocytic leukemia (CLL) and follicular non-Hodgkin's lymphoma (NHL). This paper reports an additional case of fludarabine-induced eosinophilia during the treatment of CLL. The patient, a 58-year-old man, developed peripheral eosinophilia with a peak value of 1.7×109/l 5 months after the beginning of treatment with fludarabine. A thorough investigation for other causes of eosinophilia was negative and the eosinophilia subsided after the completion of the treatment.