Inflammatory myofibroblastic tumor is a rare benign condition of unknown etiology, and may simulate malignancy. Histologically, it is composed of myofibroblasts, plasma cells and histiocytes, and is found in the lung, liver, orbit, skin, mesentery, retroperitoneum and maxillary sinus. We report a case of postoperative recurrent inflammatory myofibroblastic tumor of the retroperitoneum, occurring in a 45-year old man who complained of a palpable abdominal mass.