We describe the first case of disseminated infection with Mycobacterium genavense in an HIV-seronegative patient with a chronic haematological disorder. Our patient, an 80-year-old woman, had been under long-term treatment with chlorambucil (partially in combination with prednisone) for B-cell chronic lymphocytic leukaemia (B-CLL). When she developed general fatigue and progressive anaemia, as well as progressive lymphadenopathy and splenomegaly, bone marrow biopsy revealed granulomas with acid-fast bacilli, and cultures of both bone marrow and blood grew M. genavense. The patient's CD4+ cell count was approximately 100 microL(-1). Treatment with clarithromycin, ethambutol and rifabutin resulted in improvement of anaemia and general health as well as in regression of lymphadenopathy and splenomegaly.