A 61-year-old man developed primary adenocarcinoma with skin invasion, at the ileostomy site 33 years after a proctocolectomy for ulcerative colitis. A total of eleven patients with ileostomy adenocarcinoma have been reported in the literature. Ten patients were treated surgically for ulcerative colitis and the other for adenomatous polyposis coli. The diagnosis of stomal malignancy was made 9 to 36 years after the ileostomy (mean interval, 22 years). The pathogenesis of the malignant growth is uncertain and several possibilities are discussed: stasis, severe chronic inflammation, colonic metaplasia and severe dysplasia of the ileal mucosa. When an ileostomy requires late revision for inflammatory changes, careful pathologic examination of the entire stoma and surrounding skin is essential.