The authors report a case of Listeria monocytogenes septicemia in a pa
tient with advanced CLL after a single course of fludarabine, without
any other immunosuppressive therapy e.g. corticosteroids. The immunosu
ppressive action of fludarabine in patients who are already severely i
mmunosuppressed must be considered from a diagnostic and therapeutic p
oint of view. Listeriosis and other opportunistic infections, like pne
umocystis carinii pneumonia, have been reported during and after treat
ment with purine analogues. Prophylaxis with cotrimoxazole must theref
ore be discussed in patients with CLL treated with fludarabine.