A 73-year-old heterosexual man developed a high-grade non-Hodgkin's lymphoma at the site of an ileostomy only 2 years after proctectomy for undetermined colitis not cured by previous colectomy. In fact, the early occurrence of this usually very late and rare complication of ileostomy was probably favored by the simultaneous presence of acquired immune deficiency syndrome (AIDS) due to repeated blood transfusions for refractory anemia with excess blasts. The intestinal location of the tumor, its high-grade malignancy and B-cell origin are all features of AIDS-related non-Hodgkin's lymphoma. This case report seems to be one of the rarely identified examples of the cooperation between general predisposing factors and local irritating agents at the origin of a malignant tumor.