To demonstrate any difference in outcome between patients with carcinoma at various sites within the large bowel, analysis of a large number of patients is necessary. From the Large Bowel Cancer Project, 4292 patients have been evaluated to compare mode of presentation, surgical management, pathological findings and outcome. Carcinoma at the splenic flexure was associated with the highest risk of obstruction (49 per cent); postoperative cardiopulmonary complications (36 per cent); in-hospital mortality (18 per cent); and the lowest age-adjusted 5-year survival (28 per cent), even after curative resection (38 per cent). This survival disadvantage was seen even in those without obstruction. Further, it was not accounted for by differences in age, sex, Dukes' stage or tumour differentiation between the various sites as stratification by these variables failed to alter significance (log rank χ2= 11.1; d.f. = 4; P < 0.05). Compared with carcinoma of the left colon and rectum, tumours in the right colon were more likely to be poorly differentiated and locally advanced (in terms of fixation and penetration of the bowel wall) but were not associated with a higher risk of either distant spread at presentation or local recurrence. Age-adjusted 5-year survival following curative surgery was higher for the right colon (65 per cent) than the left (59 per cent).