A study of 391 patients with 397 colorectal lesions treated during the year 1964 revealed that the most important factors affecting prognosis are those related to early treatment when the patient was asymptomatic and the lesion was localized to the bowel. The overall hospital mortality was 4.6%. When the patient was asymptomatic, the five-year survival rate was 71% compared to 49% when symptoms were present. When the tumor was localized to the bowel wall, the rate was 63%, compared to 31% if regional or distant spread had occurred. No patients survived five years if liver metastasis was present. Lesions of the descending and sigmoid colon were associated with a better prognosis than for other anatomic segments of the colon. Patients in the fifth decade of life had a better prognosis than did patients who were younger or older.