In a large series of patients with carcinoma of the sigmoid colon and rectum there was a delay in diagnosis due to misinterpretation of the physical signs in 36 cases (2.3%). The causes of the misdiagnosis were haemorrhoids, radiological misinterpretation, and chronic inflammatory disease. A miscellaneous variety completed the series. A study of the survival of those patients in whom there was a delay in diagnosis shown that it is most unlikely that it actually affected adversely the prognosis of these patients.