Background: Referral of patients with large bowel symptoms is common and increasing. Currently most of these referrals are assessed at an outpatient clinic to determine the need and priority for investigation. Methods: Over 21 months, 1131 patients referred by the general practitioner with large bowel symptoms were randomized. Patients in the consultant-led group were assessed by surgeons with a colorectal interest while those in the open access group underwent colonoscopy if they were 55 years or older and flexible sigmoidoscopy if younger. Results: The most common symptom among referred patients was rectal bleeding (69.1 per cent) followed by change in bowel habit (48-8 per cent) and abdominal pain (32.3 per cent). There was a significant trend (P < 0.001) for patients in the consultant-led to have more investigations, and more patients in this group had no investigations (P < 0.001). Despite this, the percentage of patients with colonic or other pathology diagnosed was the same in both groups, 63.6 per cent in the consultant-led group compared with 61.8 per cent in the open access group (P = 0.558). Likewise the percentage of patients with cancer or other significant pathology was similar in both groups (13.9 versus 15.4 per cent; P = 0.532). The mean(s.d.) time to diagnose cancer or other significant pathology was 55.1(39.2) days in the consultant-led group compared with 57.4(33.6) days in the open access group (P = 0.514). The cost per patient was almost £105 more for patients in the consultant-led group. Conclusion: Patients referred by the general practitioner with large bowel symptoms should go directly to a properly managed and staffed open access large bowel investigation unit. This would enable most patients to have their investigations completed at one hospital attendance.