Mean delay between the onset of symptoms and treatment was 30.5 weeks in a hundred patients with colonic carcinoma and 38 weeks in a hundred patients with rectal carcinoma. Most of this delay occurred outside hospital and delays attributable to the patient and family doctor were almost equal in duration. Patient delay is largely the result of not knowing the importance of bowel symptoms, while delay with the family doctor was the result of not examining patients with possible rectal carcinomas and not recognising symptoms suggestive of colonic carcinoma. 42% of patients with colonic carcinoma were admitted for emergency treatment, 76% having already consulted their doctor about symptoms on one or more occasions. Hospital delay consisted mainly in waiting for investigations, poor quality barium enemas, and inadequate sigmoidoscopy. There was no relation between the duration of symptoms and the Dukes stage of the tumour.