The localization of carcinoembryonic antigen (CEA) in 78 tumors of the human colon was studied with the use of antibody to CEA in an indirect Coons test. The neoplasms differed morphologically and could be divided into two types: a) tissues in which CEA was localized in cells, and b) tissues in which malignant cells secreted CEA in greater or lesser quantity. In the first type of tissue, five forms of cells were observed: goblet-like, small vacuolar, limbic, those with intracellular accumulation of antigen, and diffuse. Tumor tissue secreting CEA could also be divided into five forms: holocrine-like, aprocrinelike, intraglandular, apical-basal, and lacunar-infiltrative. The change in CEA localization in pathologically altered cells was designated “antigenic translocation”.