Of 152 consecutive patients with carcinoma of the right colon, 61 (40 per cent) suffered delays in treatment of more than 12 weeks from the onset of symptoms, with a mean delay of 48 weeks. The most common error was failure to initiate or complete the investigation of iron-deficiency anaemia (33 patients). False-negative barium enema investigations occurred in 16 cases. Patients with delays in diagnosis had survival rates not significantly different from those who presented early. Thirty-one patients with anaemia and no abdominal symptoms had a significantly higher survival rate than 30 presenting with abdominal symptoms, despite delays in treatment (P < 0.02). Greater vigilance is required in the investigation of patients presenting with iron-deficiency anaemia.