Although resistance to Listeria monocytogenes infection requires intact T-cell mediated immunity, listeriosis is an infrequent problem in patients with HIV infection and only about 50 patients have been reported to date. Only two patients with HIV and L. monocytogenes have been attended in our hospital since the beginning of aids epidemic in 1981. Case 1: a man with HIV and 364 CD4+ cells/mm3 presented fever and occipital headache. The cerebral scan was normal and L. monocytogenes grew in licuor culture. He was outcome after treatment with ampicillin and tobramycin. Case 2: a 47 years old man with HIV, 44 CD4+ cells/mm3 and hepatic virus C cirrhosis was admitted to the hospital because fever and abdominal distension. He was on menstrual pentamidine prophylaxis for Pneumocystis carinii pneumonia (PCP). Bacterial peritonitis was diagnosed and the patient begun treatment with ceftriaxone. The patient dead 72 hours later with hepatic encepholopathy. Postmortem L. monocytogenes grew. Listeriosis is an infrequent disease in patients with HIV that causes difficult diagnostic problems, principally in patients without prophylaxis with cotrimoxazole for PCP.