Carcinoembryonic antigen (CEA) was measured in extracts of cell suspensions from tumors of the colon, stomach, breast, lung and kidney. Cell suspensions were also obtained from normal tissue surrounding the primary tumors. The number of neoplastic cells in each cell suspension was determined by cytologic criteria. Highest CEA concentrations were found in cells obtained from carcinoma of the bowel. There also appeared to be a greater difference between the concentrations of CEA in colonic tumors and either surrounding normal tissue or serum, than in tumors of other organs. There was no apparent correlation of the concentration of CEA in tumor cells and the presence or absence of metastases. The presence of CEA in normal cells from tissue adjacent to tumors was suggestive of increased synthesis of CEA by these cells in some cases.