An inflammatory myofibroblastic tumor (IMT) is a rare tumor in the abdominal cavity. A number of descriptive terms have been used to describe inflammatory tumors with myofibroblastic proliferation. The etiology and the biologic behaviors of IMTs are still unknown. Extensive pathologic examination is important to prevent misdiagnosis, and the need for long- term follow up is emphasized. Recently, we experienced a case of a huge inflammatory myofibroblastic tumor of the abdominal cavity in a young male. The patient had a painless mass in the entire abdomen. The resected specimen revealed a 15X14X12 cm3 mass involving the posterior rectus sheath, mesentery, ascending, and descending colon; and omentum. We present our experience with that along with a review of literature.