Clinical and histopathologic data from 87 patients with primary non-Hodgkin's lymphoma of the gastrointestinal (GI) tract diagnosed between 1974 and 1984 were reviewed. B-cell lymphomas of intermediate- or high-grade histology constituted 78% of lesions. Stage of disease varied with histologic grade, with a preponderance of advanced disease (stages IIIE and IV) in patients with low-grade lymphoma (15 of 21) (71%), compared with higher grade lesions (38%, P = .01). Among patients with nonlocalized (stages IIE through IV) lymphoma of intermediate- or high-grade histology, surgical resection of the primary focus afforded a higher rate of complete remission (CR) (70% v 50%) and sustained CR (61% v 21%, P = .04) after cytotoxic therapy compared with the nonresected cohort. The median survival in the resected group was 51 months + compared with 13 months in the nonresected patients (P = .012). Differences in outcome were attributable to a high risk of treatment-related complications (perforation and/or hemorrhage) (43% v 0%, P = .001) and local relapse (29% v 4%, P = .05) in nonresected individuals. Life-threatening local complications were not observed in patients with low-grade lymphoma managed solely with medical therapy. Histologic findings from surgically staged patients identified presence of extravisceral disease and intermediate- or high-grade tumor histology as features predictive of transmural invasion, enabling potential identification of patients who might be optimally managed by resection of the primary GI focus before initiation of cytotoxic therapy.