Clinical and pathologic data from 51 patients with primary sarcomas of the gastrointestinal tract treated from 1951 through 1984 were reviewed to determine clinical presentation, histologic features, treatment, and prognostic factors. The most common signs and symptoms were abdominal pain (62%), gastrointestinal bleeding (40%), and/or abdominal mass (38%). The primary site was stomach in 50%, small bowel in 30%, colorectum in 15%, and esophagus in 5%. Virtually all the sarcomas were leiomyosarcomas. Distribution was uniform among the three histologic grades; although 88% of Grade 1 tumors could be completely excised, only 35% of Grade 3 tumors could be completely resected. The 5-year survival rate was 75% for Grade 1 tumors, 16% for Grade 2 tumors, and 28% for Grade 3 tumors (p = 0.0013, Grade 1 vs. 2 and 3). Thirty of the 51 patients (59%) had curative resection with an operative morbidity rate of 24% and an operative mortality rate of 12%; at 5 years the disease-free survival rate was 58% and the overall survival rate was 63% (48% at 10 years). Eleven patients (42%) had recurrent disease develop at a median interval of 2 years after complete tumor excision. Twenty-one patients (41%) had partial excision or biopsy only of their tumors with an operative morbidity rate of 28%, operative mortality rate of 8%, and median survival of only 9 months. Overall, patients whose tumors were confined to the site of origin had a 58% 5-year survival rate compared with 20% for those whose tumors had invaded adjacent organs (p < 0.05). If the tumor was less than 10 cm in size, the 5-year survival rate was 78%, significantly better than the 38% for tumors greater than 10 cm (p = 0.03). These data suggest that histologic grade, local invasiveness, size, and extent of resection are the most important prognostic factors for patients with primary gastrointestinal sarcomas. Patients who have resection of all gross tumor, especially if it is well differentiated and localized, have a good prognosis.