Malignant lesions of the small intestine are rare, averaging only 1% of GI carcinoma. The most common primary malignancy of the small intestine is adenocarcinoma, comprising approximately 40~50% of the total malignant neoplasms of the small intestine. The most frequently affected sites are the duodenum(40%), jejunum(38%) and ileum in that order. Mortality from the malignant lesions of the small intestine is higher than that from tumors involving any other portion of the gastrointestinal tract. We have recently experienced a case of adenocarcinoma of the jejunum in a 70-y-o male patient, which herein reported and the literatures are reviewed.