A neoplasm is called metachronous if it arises as a distinct, new, primary growth after the supposedly complete removal of a similar neoplasm. The frequency of metachronous carcinoma of the colon was investigated in a series of 1,628 patients who underwent resections for primary carcinoma of the co/on during a 10-year period. In 1,100 of these cases removal was considered satisfactory and an excellent prognosis was given, but among them were 49 cases of double carcinoma and 4 of triple carcinoma. Of 77 patients who developed new lesions, 3 had had more than one carcinoma at the time of the original operation. One patient had three separate laparotomies for independent colic carcinomas. Data on the location of the lesions and their relation to polyps convince the authors that, whenever true adenomatous polyps are noted in the immediate vicinity of a carcinoma of the colon at operation, a radical procedure, such as subtotal colectomy, should be performed.