FNAB under ultrasonic guidance was performed on 14 cases with abdomical tumors of uncertain origin. All of them could not be clarified their relationship with the liver, the biliary tract, the pancreas or the alimentary tract by routine clinical exams including diagnostic imaging such as CT and Ultrasonography. Preoperating histological diagnosis has been obtained for 12 of these by FNAB, thus diagnostic rate being 85.7%. The details of tumors identified by autopsy and operations were: 3 cases of lymphoma; 3 cases of leiomyosarcoma; 4 cases of adenocarcinoma; 2 cases of hematoma; and 1 case of inflammatory mass. Non-epithelial tumor was most frequently observed. FNAB is a simple diagnostic method with high cost-effectiveness for determining the therapeutical plan for an abdominal tumor of uncertain origin which is encounted in the daily treatment.