We report a case of primary duodenal carcinoma which had partial responce by preoperative chemotherapy. A 65-year-old man visited a near clinic with the chief complaint of lower abdominal pain. Inspection, palpation and upper gastrointestinal barium studies showed that the patient had a duodenal abnormality. Ulcerative lesion of the duodenum and colon carcinoma were suspected and refersed to our hospital. After admission the abdominal tumor became larger and jaundice developed. From preoperative endoscopy of the duodenum and biopsy, malignant lymphoma was considered most probable and chemotherapy (CHOP) was started. After 2 courses of chemotherapy, significant decrease in the abdominal tumor mass was noted. Pancreatoduodenectomy with partial resection of transverse colon was performed. Postoperative course was uneventful and additional chemotherapy was done. The patient is closely followed on ambulant basis.