Chronic diarrhea due to Campylobacter jejuni has been described in patients with hypogammaglobulinemia. A patient with the acquired immune deficiency syndrome (AIDS) and normal total serum immunoglobulins had persistent diarrhea and C. jejuni on stool culture for seven and a half months despite repeated antibiotic therapy. Antibiotic sensitivity studies revealed the C. jejuni to be multiply antibiotic-resistant. Evaluation of the mechanism of resistance showed the organism harbored a conjugative plasmid capable of transferring resistance to tetracycline, but not to other antibiotics. It is concluded that C. jejuni infection may rarely result in chronic diarrhea in patients with AIDS. The combination of an immune deficiency state including abnormal B cell function previously described in AIDS and multiple antibiotic resistance may have contributed to the persistence of the organism in this case.