The term fibromatosis is characterized by an infiltrating proliferation without unequivocal neoplasma or repeated local recurrence. Fibromatosis can occur in various parts of the body such as the abdominal wall, the muscle and fascia of the extremities as well as the abdominal cavity. A 31-year-old male with attacks of abdominal pain, a feeling of fullness was referred to our hospital. On physical examination a large mass was palpable in the left abdomen. Laparotomy revealed a large mesenteric mass at the ileal region. The tumor was excised en bloc with a segment of the ileum. At this writing he is free of disease. Radiotherapy, chemotherapy and hormonal therapy have all proved to be ineffective in this disease. The only effective treatment is extensive surgical excision.