The clinical and pathologic features of 64 inflammatory fibroid polyps of the large and small bowel in 63 patients are reported. Six of the lesions in the small bowel were studied by electron microscopy. Follow-up information was obtained from 39 patients. The lesion was always benign, occurred at all ages, and had a world-wide distribution. The lesions were polypoid, sessile, originated in the submucosa, infiltrated the muscularis propria, and most closely resembled granulation tissue. The principal mesenchymal cell by electron microscopy was the fibroblast. No associated medical conditions were identified and the cause remains unknown.