Primary tumors of the small bowel are uncommon, representing less than 6 per cent of all gastrointestinal tumors and less than 2 per cent of all malignant gastrointestinal tumors. This report concerns a twenty-five year survey of our clinical records from 1946 to 1971 which revealed 140 primary small bowel tumors, excluding periampullary tumors. Fifty-two of the neoplasms (37 per cent) were benign; eighty-eight (63 per cent) were malignant and included twenty-eight adenocarcinomas (31.8 per cent), twenty-four lymphosarcomas (27.3 per cent), nineteen carcinoids (21.6 per cent), and ten leiomyosarcomas (11.4 per cent). The average age at the time of diagnosis was 56.9 years for patients with benign tumors and 55.9 years for those with malignant tumors. The illusive and obscure nature of small bowel tumors is illustrated by the fact that 63.3 per cent of patients with benign lesions and 47.6 per cent of those with malignant lesions had symptoms for more than six months before the diagnosis was made. Bleeding was the most common present complaint in patients with benign neoplasms (52.9 per cent) whereas patients with malignant lesions more often had symptoms of obstruction (50.6 per cent). Most of the benign lesions were located proximally in the small bowel (duodenum, 34.6 per cent; ileum, 11.5 per cent), and most of the malignant lesions were located distally (duodenum, 17.0 per cent; ileum, 61.4 per cent). Treatment of patients with malignant lesions was radical excision whenever possible. Adjunctive radiation therapy was used for those with lymphoma. A second benign or malignant tumor occurred in 42.9 per cent of the patients with primary small bowel tumors. The average period of survival after diagnosis of a malignant small bowel tumor was 5.03 years: for patients with adenocarcinoma, 3.6 years; lymphosarcoma, 1.3 years; carcinoid, 6.8 years; and leiomyosarcoma, 8.3 years.