Immunoproliferative small intestinal disease (IPSID) is constituted with a-heavy chain disease (a -HCD) and Mediterranean lymphoma. In contrast to western type of small intestinal lymphoma, the Mediterranean lymphoma is characterized by symptoms such as diarrhea, weight loss, malabsorption, and involvement of the distal duodenum and the upper jejunum. We present a case of the Mediterranean lymphoma. A male patient complained of diarrhea, fever, night sweats and weight loss for a year. An exploratory laparatomy revealed the small intestine to be diffusely thickened with malignant infiltration and to be perforated at one site. Jejunal resection was performed. On histologic examination, we confirmed it as malignant lymphoma of B-cell linage. This is the first case report of the Mediterranean lymphoma in Korea.