Gastrointestinal lymphoma (GIL) is rare but may be cured by surgery and chemotherapy. Because symptoms frequently mimic common abdominal conditions, presentation is often to a surgeon. Fifty-five patients with GIL were treated between 1975 and 1984: all underwent operations before the correct diagnosis was made, 22 (40%) as emergencies. Misdiagnosis in 23 (42%) led to a delay in correct treatment of greater than or equal to 6 months from the start of symptoms: in 17 (31%) the delay was greater than or equal to one year. Endoscopy and radiology were inaccurate and suggested peptic ulceration, Crohn's disease or irritable bowel syndrome. The site of disease was usually stomach and duodenum (26, 47%) or ileum and jejunum (29, 53%). The extent of surgical resection was associated with survival at greater than or equal to 3 years-in 16 (29%) who underwent 'complete resection' 14 survived, but only one of 28 survived when the operation was limited to diagnostic biopsy (P less than 0.0001). Most deaths occurred within one year of operation, commonly from perforation or haematemesis from residual mural disease during chemotherapy. In 5 of 11 patients who had biopsy only, CT scans suggested localized disease, and 'complete resection' was achieved at a second laparotomy. Complete resection should be attempted wherever possible before chemotherapy. The place for surgeons with experience is clearly central to the management of this disease.