• Analysis of data from 901 patients operated on for cancer of the colon and rectum yielded valuable diagnostic and prognostic results. Diagnostically, a palpable mass had been detectable in 55.6% of the cases in which the lesion was in the anus, rectum, or or rectosigmoid part of the colon, and 70% of all lesions of the colon and rectum were within reach of a 25-cm. (10-in.) sigmoidoscope. When the lesion was confined to the colon, it was palpable on abdominal examination in 29.6% of the cases. Prognostically, the absolute survival rate for the entire series was 43%. The operative mortality for the entire group of 901 patients was 5.6%. The average age of the 51 patients who died was 64.3 years, and this group included patients up to the age of 84. Involvement of both lymph nodes and blood vessels was a most serious prognostic sign. Patients in whom blood vessels only were involved did better than those in whom the lymph nodes only were involved; the percentages of these two groups surviving five years were 42.1 and 30.4 respectively. A few patients did well despite an unfavorable prognosis indicated by extensions and distant metastases. Thirty-six per cent of the 168 patients in whom resections were considered palliative by the operating surgeon survived more than two years. Fourteen were apparently well after five years, and, among 97 patients with proved liver metastases, 3 survived more than five years.