Primary tumors of small intestine are rarely eucountered clinically and account about for 1.5-2% of all the gastrointestinal tumors. It is quite difficult to establish the diagnosis preoperatively. In a 25-year-period from January I960 to December 1984, 45 patients with primary small bowel tumors were admitted to this institute, and their clinical data were analyzed. The rate of wrong diagnosis was 68.8% in this series as compared with 65% to 100% reported in the literature. The causes of misdiagnosis were as follows:1. There is usually no characteristic clinical sign.2. No specific diagnostic procedures are available.3. The clinicians do not have enough vigilance with this disease because of their rarity.It is emphasized that clinicians should be familar with the clinical signs and alert on the possibility of the disease.