Primary non-Hodgkin's lymphoma of the duodenum is an uncommon primary tumor of the gastrointestinal (GI) tract. Diffuse, large cell lymphoma of B-cell origin is currently recognized as representing the predominant histologic type of primary extranodal lymphoma arising in a gastrointestinal site. Three patients are presented with primary lymphoma arising in the second (two) and fourth (one) portions of the duodenum. Two patients with Stage I-E disease were treated by pancreaticoduodenectomy followed by postoperative radiotherapy, and remain without recurrence at 8 and 6 years. A third patient with Stage II-E disease of the fourth portion of the duodenum was treated with total resection of all bulky disease followed by chemotherapy without radiotherapy. However, this patient died after 46 months. The literature is reviewed, with emphasis on the use of surgical resection in the treatment of non-Hodgkin's lymphoma of the duodenum.