&NA;Malignant fibrous histiocytoma is a pleomorphic sarcoma that classically arises in the extremities and metastasizes to the lungs and regional lymph nodes. A review of the literature revealed only four previous cases of primary gastrointestinal malignant fibrous histiocytoma, all of which were treated by resection. This report describes a unique case arising in the anal sphincter that was treated by abdominoperineal resection and radiotherapy. The pathology of the condition, including immunocytochemical methods used to identify the tumor and its likely cell of origin, is discussed. The importance of long‐term follow‐up with repeated chest x‐ray andlocal lymph‐node examination is emphasized.