Between January 1985 and March 1986, five cases of listeriosis were reported in Los Angeles County in patients with the acquired immunodeficiency syndrome (AIDS). All patients were homosexual men with no other risk factors for AIDS. Two patients had sepsis only, two patients had sepsis and meningitis, and one patient had sepsis and signs of meningitis. Sixty percent of the cases (three patients) had a prior or concurrent gastrointestinal illness. Eighty percent of the cases (four patients) also had no prior history of antibiotic administration. Both of these findings may have predisposed these AIDS patients to be at increased risk for listeriosis. Although listeriosis is an infrequent illness in AIDS patients, people with AIDS or human immunodeficiency virus infection should probably refrain from ingesting food items associated with listeriosis. These food items include improperly pasteurized dairy products, and raw fruits and vegetables not properly washed.