To determine whether double-contrast barium enema (DCBE) or fibreoptic examination should be the first-line investigation for colonic disease 76 consecutive patients presenting for the first time to the outpatient clinic with symptoms of colonic disease deemed to need a DCBE after negative rigid sigmoidoscopy were entered into a trial. All underwent flexible sigmoidoscopy, then DCBE, and finally colonoscopy. 66 patients completed the study. DCBE alone gave the final diagnosis in 42 (67%) and colonoscopy alone in 60 (91%) (p = 0.0004). A combination of flexible sigmoidoscopy and DCBE led to the diagnosis in 50 patients (76%). With DCBE alone 73% of polyps and 64% of patients with inflammatory bowel disease were missed. No complications arose from the investigations. 32 (48%) patients found DCBE distressing and 15 (23%) found colonoscopy uncomfortable (p = 0.004). Its high diagnostic accuracy and relative lack of discomfort for patients make colonoscopy the primary procedure for investigating patients with large bowel symptoms referred to the general surgeon.