The objective of this study was to determine the effect of human immunodeficiency virus (HIV) infection/acquired immunodeficiency syndrome (AIDS) on inflammatory bowel disease (IBD). A retrospective survey of the medical records of St. Paul's Hospital and its AIDS-care physicians/gastroenterologists searching for patients with both HIV/AIDS and IBD was conducted. Of 1,839 hospitalized patients (4,459 hospital admissions) from 1989 to 1993, two patients with AIDS/HIV and IBD were found. The physician survey revealed four patients for a total of six patients. Four patients developed de novo IBD--two ulcerative colitis (UC), one Crohn's disease (CrD), and one indeterminate colitis (IC)--after HIV infection. Two patients had UC predating HIV seroconversion. The absolute CD4 count of patients with de novo IBD was 210-700 cells/ml at the time of IBD. The patient with IC maintained quiescent IBD from a CD4 count of 190-30 cells/ml. The other had many relapses before HIV seropositivity. With CD4 count depletion, disease activity improved. IBD medications were discontinued at a CD4 count of 130 cells/ml. Diarrhea returned at a CD4 count of 20 cells/ml; however, sigmoidoscopy was unremarkable, and mucosal biopsy revealed cryptosporidiosis without active UC. No patient had an AIDS-related illness during active IBD. Two patients followed to CD4 counts of < 30 cells/ml suffered AIDS-related infections with quiescent IBD. With a progressive decline in CD4 count, IBD disease activity may improve and remit. The CD4 count at which remission occurs may reflect severe immunodeficiency such that risk for AIDS-related infection is high. Active IBD may occur with lesser degrees of immunodeficiency.